U.S. Department of Justice

Office of Justice Programs

National Institute of Justice

Special

JULY 02

REPORT

Using DNA to Solve Cold Cases
U.S. Department of Justice

Office of Justice Programs

810 Seventh Street N.W.

Washington, DC 20531

John Ashcroft

Attorney General

Deborah J. Daniels

Assistant Attorney General

Sarah V. Hart

Director, National Institute of Justice

This and other publications and products of

the U.S. Department of Justice, Office of

Justice Programs and NIJ can be found on 

the World Wide Web at the following sites:

Office of Justice Programs

http://www.ojp.usdoj.gov

National Institute of Justice

http://www.ojp.usdoj.gov/nij

Photographs copyright © 2002 PhotoDisc, Inc.
Using DNA to Solve Cold Cases

JULY 02

NCJ 194197
This document is not intended to create, does not create, and may not be relied upon to

create any rights, substantive or procedural, enforceable at law by any party in any matter

civil or criminal.

Findings and conclusions of the research reported here are those of the authors and do not

reflect the official position or policies of the U.S. Department of Justice.

The National Institute of Justice is a component of the Office of Justice Programs, which also

includes the Bureau of Justice Assistance, the Bureau of Justice Statistics, the Office of Juvenile

Justice and Delinquency Prevention, and the Office for Victims of Crime.

Sarah V. Hart

Director

National Institute of Justice
In 1995, the National Institute of Justice

(NIJ) began research that would attempt

to identify how often DNA had exonerated

wrongfully convicted defendants. After

extensive study, NIJ published the report

Convicted by Juries, Exonerated by

Science: Case Studies in the Use of DNA

Evidence to Establish Innocence After

Trial, which presents case studies of 28

inmates for whom DNA analysis was

exculpatory.

On learning of the breadth and scope of

the issues related to forensic DNA, the

Attorney General asked NIJ to establish

the National Commission on the Future of

DNA Evidence as a means to examine the

most effective use of DNA in the criminal

justice system. The Commission was

appointed by the NIJ Director and represented the broad spectrum of the criminal

justice system. Chaired by the Honorable

Shirley S. Abrahamson, Chief Justice of

the Wisconsin Supreme Court, the Commission consisted of representatives from

the prosecution, the defense bar, law

enforcement, the scientific community,

the medical examiner community, academia, and victims’ rights organizations.

The Commission’s charge was to submit

recommendations to the Attorney General

that will help ensure the best use of DNA

as a crimefighting tool and foster its use

throughout the entire criminal justice 

system. Other focal areas for the Commission’s consideration included crime

scene investigation and evidence 

collection, laboratory funding, legal issues,

and research and development. The

Commission’s working groups, consisting

of commissioners and other experts,

researched and examined various topics

and reported back to the Commission. The

working groups’ reports were submitted

to the full Commission for approval,

amendment, or further discussion and provided the Commission with background

for its recommendations to the Attorney

General.

By nature of its representative composition

and its use of numerous working groups,

the Commission received valuable input

from all areas of the criminal justice system. The broad scope of that input enabled

the Commission to develop recommendations that both maximize the investigative

value of the technology and address the

issues raised by its application.

Commission members

Chair

The Honorable Shirley S. Abrahamson

Chief Justice

Wisconsin Supreme Court

Members

Dwight E. Adams

Director

Federal Bureau of Investigation Laboratory

iii

National Commission on the

Future of DNA Evidence
iv

SPECIAL REPORT / JULY 02

Jan S. Bashinski

Chief

Bureau of Forensic Services

California Department of Justice

Sacramento, California

George W. Clarke

Deputy District Attorney

San Diego, California

James F. Crow

Professor

Department of Genetics

University of Wisconsin

Lloyd N. Cutler

Wilmer, Cutler & Pickering Washington, D.C.

Joseph H. Davis

Former Director

Miami-Dade Medical Examiner 

Department

Paul B. Ferrara

Director

Division of Forensic Sciences

Commonwealth of Virginia

Norman Gahn

Assistant District Attorney

Milwaukee County, Wisconsin

Terrance W. Gainer

Executive Assistant Chief

Metropolitan Police Department Washington, D.C.

Terry G. Hillard

Superintendent of Police

Chicago Police Department

Chicago, Illinois

Aaron D. Kennard

Sheriff

Salt Lake County, Utah

Philip Reilly

Interleukin Genetics Waltham, Massachusetts

Ronald S. Reinstein

Associate Presiding Judge

Superior Court of Arizona

Maricopa County, Arizona

Darrell L. Sanders

Chief

Frankfort Police Department

Frankfort, Illinois

Barry C. Scheck

Professor

Cardozo Law School

New York, New York

Michael Smith

Professor

University of Wisconsin Law School

Jeffrey E. Thoma

Public Defender

Mendocino County, California

Kathryn M. Turman

Director 

Office for Victim Assistance

Federal Bureau of Investigation

William Webster

Milbank, Tweed, Hadley & McCloy Washington, D.C.

James R. Wooley

Baker & Hostetler 

Cleveland, Ohio

Commission staff

Christopher H. Asplen

Executive Director

Lisa Forman

Deputy Director

Robin W. Jones

Executive Assistant
v

USING DNA TO SOLVE COLD CASES

The Crime Scene Investigation Working

Group is a multidisciplinary group of criminal

justice professionals from across the United

States who represent both urban and rural

jurisdictions. Working group members and

contributors were recommended and

selected for their experience in the area of

criminal investigation and evidence collection from the standpoints of law enforcement, prosecution, defense, the forensic

laboratory, and victim assistance.

DNA has proven to be a powerful tool in

the fight against crime. DNA evidence can

identify suspects, convict the guilty, and

exonerate the innocent. Throughout the

Nation, criminal justice professionals are

discovering that advancements in DNA

technology are breathing new life into old,

cold, or unsolved criminal cases. Evidence

that was previously unsuitable for DNA

testing because a biological sample was

too small or degraded may now yield a

DNA profile. Development of the Combined DNA Index System (CODIS) at the

State and national levels enables law

enforcement to aid investigations by effectively and efficiently identifying suspects

and linking serial crimes to each other. The

National Commission on the Future of

DNA Evidence made clear, however, that

we must dedicate more resources to

empower law enforcement to use this

technology quickly and effectively.

Using DNA to Solve Cold Cases is intended for use by law enforcement and other

criminal justice professionals who have

the responsibility for reviewing and investigating unsolved cases. This report will

provide basic information to assist agencies in the complex process of case

review with a specific emphasis on using

DNA evidence to solve previously unsolvable crimes. Although DNA is not the

only forensic tool that can be valuable to

unsolved case investigations, advancements in DNA technology and the success

of DNA database systems have inspired

law enforcement agencies throughout the

country to reevaluate cold cases for DNA

evidence. As law enforcement professionals progress through investigations, however, they should keep in mind the array of

other technology advancements, such as

improved ballistics and fingerprint databases, which may substantially advance

a case beyond its original level.

Chair

Terrance W. Gainer

Executive Assistant Chief

Metropolitan Police Department

Washington, D.C. 

Members

Susan Ballou

Office of Law Enforcement Standards

National Institute of Standards and 

Technology

Gaithersburg, Maryland

Jan S. Bashinski

Chief

Bureau of Forensic Services

California Department of Justice

Sacramento, California

Sue Brown

INOVA Fairfax Hospital 

SANE Program

Falls Church, Virginia

Crime Scene Investigation 

Working Group
vi

SPECIAL REPORT / JULY 02

Lee Colwell

Director

Criminal Justice Institute

University of Arkansas System

Little Rock, Arkansas

Thomas J. Cronin

Chief

City of Coeur d’Alene Police Department

Coeur d’Alene, Idaho

Terry G. Hillard

Superintendent of Police

Chicago Police Department

Chicago, Illinois

Mark Johnsey

Master Sergeant (Ret.)

Division of Forensic Services

Illinois State Police Department

Springfield, Illinois

Christopher Plourd

Attorney at Law 

San Diego, California

Darrell L. Sanders

Chief

Frankfort Police Department

Frankfort, Illinois

Clay Strange

Assistant District Attorney

Travis County District Attorney’s Office

Austin, Texas

Contributors

Cheryl May

Assistant Director

Forensic Sciences Education Center

Little Rock, Arkansas

William McIntyre

Detective Sergeant (Ret.)

Atlantic County Prosecutor’s Office

Homicide Unit

Hammonton, New Jersey
vii

National Commission on the Future of DNA Evidence . . . . . . . . . . . . . . . . . . . . . iii

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

The Long and Short of DNA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

How Can DNA Databases Aid Investigations? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Practical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Identifying, Analyzing, and Prioritizing Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Contents
In 1990, a series of brutal attacks on elderly victims occurred in Goldsboro, North

Carolina, by an unknown individual dubbed

the “Night Stalker.” During one such

attack in March, an elderly woman was

brutally raped and almost murdered. Her

daughter’s early arrival home was the only

thing that saved the woman’s life. The

suspect fled, leaving behind materials

intended to burn the residence and the

victim in an attempt to conceal the crime.

In July 1990, another elderly woman was

brutally raped and murdered in her home.

Three months later, a third elderly woman

was raped and stabbed to death. Her husband was also murdered. Their house

was burned in an attempt to cover up the

crime, but fire/rescue personnel pulled

the bodies from the house before it was

engulfed in flames.

When DNA analysis was conducted on

biological evidence collected from vaginal

swabs from each victim, authorities concluded that the same perpetrator had

committed all three crimes. However,

there was no suspect. 

For 10 years, both the Goldsboro Police

Department and the crime laboratory

refused to forget about these cases. With

funding from the National Institute of

Justice, the crime laboratory retested the

biological evidence in all three cases with

newer DNA technology and entered the

DNA profiles into North Carolina’s DNA

database. This would allow the DNA profile developed from the crime scene evidence to be compared to thousands of

convicted offender profiles already in the

database. 

In April 2001, a “cold hit” was made to

the perpetrator’s convicted offender DNA

profile in the database. The perpetrator

had been convicted of shooting into an

occupied dwelling, an offense that

requires inclusion in the North Carolina

DNA database. The suspect was brought

into custody for questioning and was

served with a search warrant to obtain a

sample of his blood. That sample was analyzed and compared to the crime scene

evidence, thereby confirming the DNA

database match. When confronted with

the DNA evidence, the suspect confessed

to all three crimes.

Mark Nelson, special agent in charge of

the North Carolina State Crime Laboratory,

said, “Even though these terrible crimes

occurred more than 10 years ago, we

never gave up hope of solving them one

day.” 

Every law enforcement department

throughout the country has unsolved

cases that could be solved through recent

advancements in DNA technology. Today,

investigators who understand which evidence may yield a DNA profile can identify

a suspect in ways previously seen only on

television. Evidence invisible to the naked

eye can be the key to solving a residential

burglary, sexual assault, or murder. The

saliva on the stamp of a stalker’s threatening letter, the perspiration on a rapist’s

mask, or the skin cells shed on the ligature of a strangled child may hold the key

to solving a crime.

In Austin, Texas, for example, an investigator knowledgeable about DNA technology was able to solve the rape of a local

college student. Having read about the

potential for obtaining DNA evidence from

the ligature used to strangle a victim, the

investigator requested DNA testing on the

phone cord used to choke the victim in his

case. He realized that in the course of

1

Introduction
2

SPECIAL REPORT / JULY 02

choking someone, enough force and friction is applied to the rope or cord that the

perpetrator’s skins cells may rub off his

hands and be left on the ligature.

The investigator’s request paid off in an

unanticipated way. In spite of the attacker’s attempt to avoid identification through

DNA evidence by wearing both a condom

and rubber gloves, a reliable DNA profile

was developed from the evidence. During

the struggle, the attacker was forced to

use one hand to hold the victim down,

leaving only one hand to pull the phone

cord tight. The attacker had to grab the

remaining end of the cord with his mouth,

thereby depositing his saliva on the cord.

Although the developed profile came from

saliva rather than skin, DNA not only

solved the case in Austin, but also linked

the perpetrator to a similar sexual assault

in Waco.

Without the investigator’s understanding

of DNA technology and where DNA might

be found, the case may have gone

unsolved. The successful review and

investigation of unsolved cases require

the same basic elements as the investigation of new cases: cooperation among law

enforcement, the crime laboratory, and

the prosecutor’s office. Investigators

should be aware of technological

advances in DNA testing that may yield

profiles where previous testing was not

performed or was unsuccessful. The

crime laboratory can be essential to the

preliminary review of unsolved cases, for

example, by providing investigators with

laboratory reports from previous testing

and consultation regarding the investigative value of new DNA analysis techniques

and DNA database search capabilities.

Additionally, the prosecutor’s office should

be involved as soon as a case is reopened

so that legal issues are addressed appropriately. It is also extremely important that

case reconstruction considers the victim

or victim’s family and the importance of

finality to closing a case.

Although DNA is not the only forensic tool

available for the investigation of unsolved

cases, advancements in DNA testing and

the success of DNA database systems

have inspired law enforcement agencies

throughout the country to reevaluate

cases previously thought unsolvable. The

purpose of this report is to provide law

enforcement with a practical resource for

the review of old, cold, or unsolved cases

that may be solved through DNA technology and DNA databases. “The Long and

Short of DNA” and “How Can DNA

Databases Aid Investigations?” will educate the reader about the science and

technology of DNA testing and DNA databases. “Practical Considerations” provides

important background information on legal

and practical considerations regarding the

application of DNA technology to old, cold,

or unsolved cases. Finally, a step-by-step

process is provided to help investigators

select cases that would most likely be

solved with DNA evidence. As investigators advance through this process, they

should also keep in mind the array of

other technology advancements, such as

improved ballistics and fingerprint databases, that may benefit their investigation.

Advancements in 

DNA technology

Advancements in DNA analysis, together

with computer technology and the

Combined DNA Index System (CODIS),1

have created a powerful crimefighting tool

for law enforcement. CODIS is a computer network that connects forensic DNA

laboratories at the local, State, and national levels. DNA database systems that use

CODIS contain two main criminal indexes

and a missing persons index. When a

DNA profile is developed from crime

scene evidence and entered into the

forensic (crime scene) index of CODIS,

the database software searches thousands of convicted offender DNA profiles

The successful

review and

investigation of

unsolved cases

require cooperation among law

enforcement, the

crime laboratory,

and the prosecutor’s office.
3

USING DNA TO SOLVE COLD CASES

(contained in the offender index) of individuals convicted of offenses such as rape

and murder. Similar to the Automated

Fingerprint Identification System (AFIS),

CODIS can aid investigations by efficiently

comparing a DNA profile generated from

biological evidence left at a crime scene

against convicted offender DNA profiles

and forensic evidence from other cases

contained in CODIS. CODIS can also aid

investigations by searching the missing

persons index, which contains DNA profiles of unidentified remains and DNA profiles of relatives of those who are missing.

Because of the recidivistic nature of violent offenders, the power of a DNA database system is evident not only in the

success of solving crimes previously

thought unsolvable, but perhaps more

importantly, through the prevention of

crime.

When properly documented, collected, and

stored, biological evidence can be analyzed

to produce a reliable DNA profile years,

even decades, after it is collected. Just as

evidence collected from a crime that

occurred yesterday can be analyzed for

DNA, today evidence from an old rape kit,

bloody shirt, or stained bedclothes may

contain a valuable DNA profile. These new

analysis techniques, in combination with an

evolving database system, make a powerful

argument for the reevaluation of unsolved

crimes for potential DNA evidence.

Knowledgeable law enforcement officers

are taking advantage of powerful DNA

analysis techniques by investigating crime

scenes with a keener eye toward biological evidence. The same new approach

being applied to crime scene processing

and current case investigation can be

applied to older unsolved cases. Law

enforcement agencies across the country

are establishing cold-case squads to systematically review old cases for DNA and

other new leads. This report will serve as

a resource to assist law enforcement with

maximizing the potential of DNA evidence

in unsolved cases by covering the basics

of DNA analysis and its application to

forensic casework. The report will also

demonstrate how DNA database systems,

advancing technology, and cooperative

efforts can enhance unsolved case investigative techniques.

New laws

Advancements in DNA technology have

led to significant changes in many States’

statutes, which may affect the manner in

which unsolved cases are investigated,

filed, and prosecuted. Advancements in

the technology have been so significant

that laws are being created, amended, and

even repealed to take advantage of its

ability to identify and convict the guilty and

exonerate the innocent. Laws regarding

DNA admissibility in court, its use in postconviction appeals, the creation and

expansion of databases, and the extension

or elimination of statutes of limitation are

examples of the quickly evolving impact of

DNA on the criminal justice system. Given

the legal changes occurring throughout

the country, constant contact and consultation with the local prosecutor is critical

not only for the investigation of older

cases but for all cases in which DNA may

be relevant evidence.

Statutes of limitation

Statutes of limitation may be one of the

most difficult issues to overcome when

examining older cases. Statutes of limitation establish time limits under which

criminal charges can be filed for a particular offense. These statutes are rooted in

the protection of individuals from the use

of evidence that becomes less reliable

over time. For example, witnesses’ memories fade as time goes by. However,

although some evidence, such as eyewitness accounts, can lose credibility over

time, DNA evidence has the power to

determine truth 10, 15, even 20 years

The power of a

DNA database

system is evident

not only in the

success of

solving crimes

previously thought

unsolvable, but

through the

prevention

of crime.
4

SPECIAL REPORT / JULY 02

after an offense is committed. States are

beginning to realize that the reliability of

DNA technology may necessitate the

reevaluation of statutes of limitation in the

filing of cases.

Database expansion

The use of DNA evidence and convicted

offender DNA databases has expanded

significantly since the first U.S. DNA database was created in 1989. Although State

and local DNA databases established in

the early 1990s contained only DNA profiles from convicted murderers and sex

offenders, the undeniable success of DNA

databases has resulted in a national trend

toward database expansion. All States

require at least some convicted offenders

to provide a DNA sample to be collected

for DNA profiling and, in 2000, the Federal

Government began requiring certain

offenders convicted of Federal or military

crimes to also provide a DNA sample for

the criminal DNA database. Recognizing

that the effectiveness of the DNA database relies on the volume of data contained in both the forensic index (crime

scene samples) and the convicted offender index of CODIS, many States are

changing their database statutes to

include less violent criminals. Many

States are enacting legislation to require

all convicted felons to submit a DNA profile to the State database. The tendency

for States to include all convicted felons in

their databases dramatically increases the

number of convicted offender DNA profiles against which forensic DNA evidence

can be compared, thus making the database system a more powerful tool for law

enforcement.

New legal approaches

DNA technology and DNA databases have

encouraged the development of new

approaches to old cases. One such

approach is the filing of charges by “John

Doe” warrant. These warrants are based

on the unique DNA profile obtained from

the analysis of unsolved crime scene evidence. Although John Doe warrants are

traditionally filed based on the physical

description or alias of an unnamed suspect, investigators and prosecutors are

now filing charges using the suspect’s

DNA profile as the identifier. This innovative approach has allowed charges to be

filed that toll and permit old cases to be

prosecuted when the person matching the

John Doe DNA profile is identified. John

Doe DNA warrants are one way to permit

cases to remain active, allowing them the

chance to be solved through the DNA

database in the future.

The reliability of

DNA technology

may necessitate

the reevaluation

of statutes

of limitation.
5

DNA is the fundamental building block for

an individual’s entire genetic makeup. It is

a component of virtually every cell in the

human body, and a person’s DNA is the

same in every cell. That is, the DNA in a

person’s blood is the same as the DNA in

his skin cells, saliva, and other biological

material.

DNA analysis is a powerful tool because

each person’s DNA is unique (with the

exception of identical twins). Therefore,

DNA evidence collected from a crime

scene can implicate or eliminate a suspect, similar to the use of fingerprints. It

also can analyze unidentified remains

through comparisons with DNA from relatives. Additionally, when evidence from

one crime scene is compared with evidence from another using CODIS, those

crime scenes can be linked to the same

perpetrator locally, statewide, and 

nationally.

DNA is also a powerful tool because when

biological evidence from crime scenes is

collected and stored properly, forensically

valuable DNA can be found on evidence

that may be decades old. Therefore, old

cases that were previously thought unsolvable may contain valuable DNA evidence

capable of identifying the perpetrator.

Similar to fingerprints

DNA is often compared with fingerprints

in the way matches are determined.

When using either DNA or fingerprints to

identify a suspect, the evidence collected

from the crime scene is compared with a

“known” standard. If identifying features

are the same, the DNA or fingerprint can

be determined to be a match. However, if

identifying features of the DNA profile or

fingerprint are different from the known

standard, it can be determined that it did

not come from that known individual.

DNA technology 

advancements

Recent advancements in DNA technology

have improved law enforcement’s ability

to use DNA to solve old cases. Original

forensic applications of DNA analysis were

developed using a technology called

restriction fragment length polymorphism

(RFLP). Although very old cases (more

than 10 years) may not have had RFLP

analysis done, this kind of DNA testing

may have been attempted on more recent

unsolved cases. However, because RFLP

analysis required a relatively large quantity

of DNA, testing may not have been successful. Similarly, biological evidence

deemed insufficient in size for testing may

not have been previously submitted for

testing. Also, if a biological sample was

degraded by environmental factors such

as dirt or mold, RFLP analysis may have

been unsuccessful at yielding a result.

Newer technologies could now be successful in obtaining results. 

Newer DNA analysis techniques enable

laboratories to develop profiles from biological evidence invisible to the naked eye,

such as skin cells left on ligatures or

weapons. Unsolved cases should be evaluated by investigating both traditional and

nontraditional sources of DNA. Valuable

DNA evidence might be available that previously went undetected in the original

investigation.

If biological evidence is available for testing or retesting in unsolved case investigations, it is important that law enforcement

and the crime laboratory work together

to review evidence. Logistical issues

The Long and Short of DNA

If biological

evidence is 

available for

testing or 

retesting in

unsolved case

investigations, it

is important that

law enforcement

and the crime

laboratory work

together to

review evidence.
6

SPECIAL REPORT / JULY 02

regarding access to and the cost of DNA

analysis will be a factor, as well as issues

that relate to the discriminating power of

each technology and that might affect the

outcome of the results. Laboratory personnel can also provide a valuable perspective on which evidence might yield

valuable and probative DNA results.

Finally, if previously tested biological evidence produced a DNA profile but excluded the original suspect, revisiting those

“exclusion” cases in the context of comparing them with DNA databases might

prove to be very valuable to solving old

cases.

PCR analysis 

PCR (polymerase chain reaction) enhances

DNA analysis and has enabled laboratories

to develop DNA profiles from extremely

small samples of biological evidence. The

PCR technique replicates exact copies of

DNA contained in a biological evidence

sample without affecting the original,

much like a copy machine. RFLP analysis

requires a biological sample about the size

of a quarter, but PCR can be used to

reproduce millions of copies of the DNA

contained in a few skin cells. Since PCR

analysis requires only a minute quantity of

DNA, it can enable the laboratory to analyze highly degraded evidence for DNA.

On the other hand, because the sensitive

PCR technique replicates any and all of

the DNA contained in an evidence sample,

greater attention to contamination issues

is necessary when identifying, collecting,

and preserving DNA evidence. These factors may be particularly important in the

evaluation of unsolved cases in which evidence might have been improperly collected or stored. 

STR analysis

Short tandem repeat (STR) technology is a

forensic analysis that evaluates specific

regions (loci) that are found on nuclear

DNA. The variable (polymorphic) nature of

the STR regions that are analyzed for

forensic testing intensifies the discrimination between one DNA profile and another. For example, the likelihood that any

two individuals (except identical twins) will

have the same 13-loci DNA profile can be

as high as 1 in 1 billion or greater. The

Federal Bureau of Investigation (FBI) has

chosen 13 specific STR loci to serve as

the standard for CODIS. The purpose of

establishing a core set of STR loci is to

ensure that all forensic laboratories can

establish uniform DNA databases and,

more importantly, share valuable forensic

information. If the forensic or convicted

offender CODIS index is to be used in the

investigative stages of unsolved cases,

DNA profiles must be generated by using

STR technology and the specific 13 core

STR loci selected by the FBI.

Mitochondrial DNA analysis

Mitochondrial DNA (mtDNA) analysis

allows forensic laboratories to develop

DNA profiles from evidence that may not

be suitable for RFLP or STR analysis.

While RFLP and PCR techniques analyze

DNA extracted from the nucleus of a cell,

mtDNA technology analyzes DNA found in

a different part of the cell, the mitochondrion (see exhibit 1). Old remains and evidence lacking nucleated cells—such as

hair shafts, bones, and teeth—that are

unamenable to STR and RFLP testing may

yield results if mtDNA analysis is performed. For this reason, mtDNA testing

can be very valuable to the investigation of

an unsolved case. For example, a cold

case log may show that biological evidence in the form of blood, semen, and

hair was collected in a particular case, but

that all were improperly stored for a long

period of time. Although PCR analysis

sometimes enables the crime laboratory

to generate a DNA profile from very

degraded evidence, it is possible that the

blood and semen would be so highly

degraded that nuclear DNA analysis would

not yield a DNA profile. However, the hair

If the convicted

offender or

forensic index

of CODIS is to

be used in the

investigative

stages of an

unsolved case,

DNA profiles must

be generated

using STR

analysis.

Fingerprints DNA Strands
7

USING DNA TO SOLVE COLD CASES

shaft could be subjected to mtDNA analysis and thus be the key to solving the

case. Finally, it is important to note that all

maternal relatives (for example, a person’s

mother or maternal grandmother) have

identical mtDNA. This enables unidentified

remains to be analyzed and compared to

the mtDNA profile of any maternal relative

for the purpose of aiding missing persons

or unidentified remains investigations.

Although mtDNA analysis can be very

valuable to the investigation of criminal

cases, laboratory personnel should always

be involved in the process.

Exhibit 1. Cell diagram

Mitochondrion

Nucleus

Chromosomes

Y-chromosome analysis

Several genetic markers have been identified on the Y chromosome that can

be used in forensic applications. Ychromosome markers target only the

male fraction of a biological sample.

Therefore, this technique can be very 

valuable if the laboratory detects complex

mixtures (multiple male contributors) within a biological evidence sample. Because

the Y chromosome is transmitted directly

from a father to all of his sons, it can also

be used to trace family relationships

among males. Advancements in Y-chromosome testing may eventually eliminate the

need for laboratories to extract and separate semen and vaginal cells (for example,

from a vaginal swab of a rape kit) prior to

analysis. 

Cooperative efforts with the crime laboratory are essential to deciding which analysis methods will be most valuable in a

particular case. It is important to note,

however, that while RFLP and mtDNA testing may be valuable to the investigation of

an old case, current DNA databases are

being populated with DNA profiles that are

generated using STR analysis. RFLP and

mtDNA profiles are not compatible with

the convicted offender or forensic indexes

of CODIS.2
9

The development and expansion of databases that contain DNA profiles at the

local, State, and national levels have greatly enhanced law enforcement’s ability to

solve cold cases with DNA. Convicted

offender databases store hundreds of

thousands of potential suspect DNA 

profiles, against which DNA profiles 

developed from crime scene evidence

can be compared.

Given the recidivistic nature of many

crimes, such as sexual assault and burglary, a likelihood exists that the individual

who committed the crime being investigated was convicted of a similar crime and

already has his or her DNA profile in a

DNA database that can be searched by

CODIS. Moreover, CODIS also permits the

cross-comparison of DNA profiles developed from biological evidence found at

crime scenes. Even if a perpetrator is not

identified through the database, crimes

may be linked to each other, thereby aiding an investigation, which may eventually

lead to the identification of a suspect. 

What is CODIS?

CODIS is a computer software program

that operates local, State, and national

databases of DNA profiles from convicted

offenders, unsolved crime scene evidence, and missing persons. Every State

in the Nation has a statutory provision for

the establishment of a DNA database that

allows for the collection of DNA profiles

from offenders convicted of particular

crimes. CODIS software enables State,

local, and national law enforcement crime

laboratories to compare DNA profiles electronically, thereby linking serial crimes to

each other and identifying suspects by

matching DNA profiles from crime scenes

with profiles from convicted offenders.

The success of CODIS is demonstrated by

the thousands of matches that have linked

serial cases to each other and cases that

have been solved by matching crime

scene evidence to known convicted

offenders. 

The missing persons index consists of the

unidentified persons index and the reference index. The unidentified persons

index contains DNA profiles from recovered remains, such as bone, teeth, or hair.

The reference index contains DNA profiles

from related individuals of missing persons so that they can be periodically compared to the unidentified persons index.

All samples for this index are typed using

mtDNA and STR DNA analysis (if possible)

to maximize the power of advancing 

technology. 

How Can DNA Databases 

Aid Investigations?

SUCCESS STORY

A “forensic hit” occurred in the National DNA Index System (NDIS) that linked

a dead Florida man’s DNA profile to eight serial unsolved rapes in Washington,

D.C. and three offenses in Florida.

In 1999, Leon Dundas was killed in a drug deal. Investigators remembered

Dundas refusing to give a blood sample in connection with a rape investigation

in 1998. They were able to obtain Dundas’ blood sample through the medical

examiner’s office and forwarded it to the DNA lab at the Florida Department of

Law Enforcement. Dundas’ DNA profile was compared with the national forensic index and a match was made between Dundas and DNA evidence from a

rape victim in Washington, D.C. 

The FBI then entered DNA evidence from additional unsolved rapes committed

in Washington. Dundas’ DNA matched seven additional rapes in Washington

and three more in Jacksonville, Florida. Police in Washington said that without

DNA, they would have never identified Dundas, who had no prior recorded history of violent crime.
10

SPECIAL REPORT / JULY 02

How does CODIS work?

CODIS uses two indexes to generate

investigative leads in crimes for which biological evidence is recovered from a crime

scene. The convicted offender index contains DNA profiles of individuals convicted

of certain crimes ranging from certain 

misdemeanors to sexual assault and murder. Each State has different “qualifying

offenses” for which persons convicted of

them must submit a biological sample for

inclusion in the DNA database. The forensic index contains DNA profiles obtained

from crime scene evidence, such as

semen, saliva, or blood. CODIS uses 

computer software to automatically

search across these indexes for a potential match. 

A match made between profiles in the

forensic index can link crime scenes to

each other, possibly identifying serial

offenders. Based on these “forensic hits,”

police in multiple jurisdictions or States

can coordinate their respective investigations and share leads they have developed

independent of each other. Matches made

between the forensic and convicted

offender indexes can provide investigators

with the identity of a suspect(s). It is

important to note that if an “offender hit”

is obtained, that information typically is

used as probable cause to obtain a new

DNA sample from that suspect so the

match can be confirmed by the crime laboratory before an arrest is made.

LDIS, SDIS, and NDIS

CODIS is implemented as a distributed

database with three hierarchical levels (or

tiers)—local, State, and national. All three

levels contain forensic and convicted

offender indexes and a population file

(used to generate statistics). The hierarchical design provides State and local laboratories with the flexibility to configure

CODIS to meet their specific legislative

and technical needs. 

A description of the three CODIS tiers 

follows (see exhibit 2).

■ Local. Typically, the Local DNA Index

System (LDIS) installed at crime laboratories is operated by police departments

or sheriffs’ offices. DNA profiles originated at the local level can be transmitted to the State and national levels.

■ State. Each State has a designated laboratory that operates the State DNA

Index System (SDIS). SDIS allows local

laboratories within that State to compare DNA profiles. SDIS also is the communication path between the local and

national tiers. SDIS is typically operated

by the agency responsible for implementing and monitoring compliance

with the State’s convicted offender

statute. 

■ National. The National DNA Index

System (NDIS) is the highest level of

the CODIS hierarchy and enables qualified State laboratories that are actively

participating in CODIS to compare

DNA profiles. NDIS is maintained by

the FBI under the authority of the DNA

Identification Act of 1994.

Limitations of using the

DNA database

The more data contained in the forensic

and offender indexes of CODIS, the more

powerful a tool it becomes for law

enforcement, especially in its application

to unsolved case investigation. However,

because many jurisdictions are in the

process of developing and populating their

DNA databases, convicted offender and

forensic casework backlogs have been

created over time and continue to grow

for several reasons. First, as States recognize the crime-solving potential of DNA

databases, they continue to expand

the scope of their convicted offender 

legislation, which increases the number of

The offender

index contains

DNA profiles

of individuals

convicted of

certain crimes.

The forensic index

contains DNA

profiles obtained

from crime

scene evidence.
11

USING DNA TO SOLVE COLD CASES

Exhibit 2. CODIS tiers

samples to be collected and analyzed by

the DNA laboratory. As a result, more than

1 million uncollected convicted offender

DNA profiles are “owed” to the system. 

An equally important but more difficult

problem to quantify is that of unprocessed

casework that contains biological evidence. This casework backlog may include

nonsuspect or unsolved cases that could

be analyzed and solved as a result of

advancements in DNA technology.

Convicted offender backlogs

Although all 50 States have passed DNA

database legislation, many States have

backlogs of convicted offender samples

that have been collected but have not yet

been analyzed. Although Federal funding

has played an important role in reducing

existing backlogs, the crimefighting potential of DNA has prompted many States to

revise their statutes to require nonviolent

convicted offenders to provide a DNA

sample for analysis and upload into

CODIS. The trend toward expanding convicted offender DNA statutes to include

nonviolent offenders has significantly

increased the number of DNA samples

requiring collection and analysis. Although

the success of using the DNA database as

a crime-solving and crime-prevention tool

can easily be demonstrated once convicted offender backlogs are reduced, it

should be recognized that new backlogs
12

SPECIAL REPORT / JULY 02

are instantly created by the passage of

expanded DNA legislation laws. Convicted

offender backlogs are an ongoing logistical

issue that can compound the complexity

of investigating cold cases by using the

DNA database.

Forensic casework backlogs

Addressing issues that affect the efficient

and effective use of DNA databases in the

United States is complicated further by

the existence of casework backlogs. This

refers to biological evidence in perhaps

tens of thousands of criminal cases,

including violent and nonviolent crimes,

that has not been tested or retested for

DNA. 

Unprocessed rape kits are a clear example

of this kind of backlog. Despite the established fact that rape typically yields biological evidence, as of October 1999, at least

180,000 rape kits remained on shelves

across the country, unprocessed, because

no suspects have been identified. The

DNA evidence from these and other criminal cases often is not analyzed and

entered into the DNA database because

forensic laboratories have to prioritize their

work and cases scheduled for trial take

precedence over cases in which no suspect is known. In most jurisdictions, nonsuspect criminal cases that contain

biological evidence are not being analyzed

and entered into the DNA database. In

many jurisdictions, DNA from crime

scenes is still primarily used to prosecute

offenders, not to investigate crimes. The

convicted offender backlog and limited

resources for casework going to trial preclude State forensic laboratories from analyzing all biological evidence for DNA,

which in turn prevents law enforcement

from being able to realize the full crimesolving potential of CODIS.

The backlog of forensic cases has practical

consequences for most law enforcement

agencies in the United States. Laboratory

capacity limitations result in the ability to

process crime scene samples from only

the most serious of offenses. More and

more, however, agencies such as those in

the United Kingdom are discovering the

value of DNA technology in solving property crimes. Blood left on a broken apartment window or saliva found on a

discarded beer bottle can be used to

identify burglars, and the skin cells rubbed

off onto the steering wheel of a stolen

vehicle can solve car thefts. However, as

long as forensic laboratories remain able

to process only the most serious cases,

the full potential of DNA technology to

solve crime will remain untapped.
13

A broad range of considerations must be

made long before any DNA testing is actually attempted in older, unsolved cases.

These include—

■ Legal considerations, such as the application or expiration of statutes of limitation.

■ Technological considerations, such as

the nature and condition of the evidence

as originally collected, stored, and in

some instances, subjected to other

forensic tests. 

■ Practical considerations, such as the

availability of witnesses in the event

DNA testing would identify a suspect

and lead to an arrest and a trial. 

■ Resource issues, such as the time and

money available for investigation and

forensic analysis.

The nature and scope of these issues

require that any approach to reexamining

old cases for potential DNA evidence be

collaborative, whether by an individual

investigator or by a specialized unit developed specifically for cold case review.

Local prosecutors can provide valuable

insight into legal issues that might prevent

or help a future prosecution. Victim/witness

units or advocates can provide valuable

assistance with locating, educating, and

encouraging witnesses. Consultation with

representatives from the crime laboratory

is critical to ensuring that potential DNA

evidence can be successfully analyzed. 

Evidence considerations

When collecting unsolved case evidence

from storage facilities, the case investigator should be ready to handle all types of

packaging disasters. Evidence may be

stored in heavy-duty plastic bags, stapled

shut as the past form of “sealing.”

Multiple items may be sealed in one plastic bag, or even unpackaged in large,

open, cardboard boxes. Unprotected

microscope slides from medical facilities

might also be found as a result of investigating old cases. No attempt should be

made on the part of the investigator to

separate and repackage evidence. The

condition and position that the evidence

has been stored in could provide valuable

clues to the forensic scientist for testability of evidence. Only when evidence is

found unpackaged should the investigator

properly package and label the item(s) to

minimize the possibility for contamination

from that point forward. It is important

that any evidence items are handled minimally and only by individuals wearing disposable gloves. As always, it is also very

important that all actions taken as a result

of opening, evaluating, packaging, or

repackaging evidence are documented

thoroughly in the case folder. 

Degraded evidence

Prior to the frequent use of DNA technology, biological evidence may have been 

collected and stored in ways that were not

necessarily the best methods for preserving samples for future DNA testing. For

example, evidence containing biological

fluids that were originally collected for

ABO Blood Typing analysis or other serology methods may have been packaged or

stored in ways that can limit DNA testing.

Some methods of collection and storage

may promote the growth of bacteria and

mold on the evidence. Bacteria can seriously damage or degrade DNA contained

in biological material and inhibit the ability

to develop a DNA profile; however, evidence can still sometimes yield DNA

results. For example, PCR technology can

allow the laboratory to develop profiles

Local prosecutors

can provide

valuable insight

into legal issues.

Victim/witness

units or advocates

can help locate,

educate, and

encourage

witnesses. Consultation with

representatives

from the crime

laboratory is

critical. 

Practical Considerations
from some moldy biological samples,

whereas other evidence may fail to yield a

usable DNA profile, even when no mold is

visible. Therefore, close consultation with

the laboratory is important to determine

the type of DNA testing most likely to

yield results on the available evidence. 

Contamination issues

Because of the particularly sensitive

nature of DNA technology, the potential

contamination of evidence should be carefully considered. Technologies used to

analyze evidence prior to the forensic

application of DNA were not always sensitive to contaminants. Evidence in older

cases may have been collected in ways

that lacked appropriate contamination or

cross-contamination safeguards, which

can make the DNA results less useful or

even misleading. In these cases, clarifying

results by identifying the contributor of an

additional profile can determine whether

the DNA results may now be used. When

a mixture is detected, a careful reconstruction of the evidence collection, storage, and analysis process must be

undertaken. It may be determined that

DNA profiles will be required from onscene officers, evidence technicians, or

laboratory scientists who had access to

the evidence for comparison with evidence results. In these instances, proper

chain-of-custody reconstruction is critical.

It is also important to avoid contamination

when handling biological evidence during

the course of the current review. If evidence that may contain biological material

is already sealed, do not reopen it before

sending it to the laboratory. (See Evidence

Handling Recommendations.)

Legal considerations

Numerous legal issues might arise when

examining older cases for potential DNA

evidence. These issues are most likely

jurisdictionally specific and may differ from

State to State. Although most jurisdictions

maintain no statute of limitation for filing

charges in a homicide case, States can

vary widely in the time allowed for filing

charges in other cases, such as rape and

other sexual assault crimes. Furthermore,

in recognition of DNA technology’s ability

to solve old cases, many States are

extending or even eliminating statutes

of limitation for certain crimes. 

Chain of custody

When a case remains unsolved for a long

period of time, evidence is usually handled

by an increased number of individuals.

Many unsolved cases to be reviewed for

DNA evidence may have been previously

reinvestigated or handled by several different investigators as a result of new leads

or periodic, systematic reviews. Furthermore, as cases age, the likelihood increases that evidence may be moved to new or

remote storage locations as evidence

from newer cases fills police department

shelves. 

Many cases may also have had evidence

submitted to the laboratory for various

forms of forensic testing. Evidence in

older cases may have been submitted for

standard serological testing, but can now

be tested for DNA with much greater success. Hair previously submitted for standard microscopic hair analysis may now

14

SPECIAL REPORT / JULY 02

EVIDENCE HANDLING RECOMMENDATIONS

■ Wear gloves. Change them between handling each item of evidence.

■ Use disposable instruments or clean instruments thoroughly before and 

after handling each evidence sample.

■ Avoid touching the area where you believe DNA may exist.

■ Avoid touching your face, nose, and mouth when examining and repackaging

evidence. 

■ Put dry evidence into new paper bags or envelopes; do not use plastic bags.

■ Do not use staples.

■ If repackaging of evidence is necessary, consult with laboratory personnel.
be submitted for mtDNA testing. As with

all criminal investigations, chain-of-custody

issues are critical to maintaining the

integrity of the evidence. In all cases, the

ultimate ability to use DNA evidence will

depend on the ability to prove that the

chain of custody was maintained.

Statutes of limitation

One of the first issues to address when

reviewing an unsolved case is whether

the statutes of limitation on a case have

run out. Several considerations arise when

addressing a statute of limitation issue.

Good communication between law enforcement and local prosecutors is critical

when examining these legal questions.

Changes in statutes. Advances in DNA

technology and the creation of DNA databases are leading many criminal justice

professionals to rethink time limits placed

on the filing of criminal charges. Because

biological evidence can yield reliable DNA

analysis results years after the commission of a crime, many State legislatures

have begun to extend, and in some

cases eliminate, the statutes of limitation

for some crimes and in certain circumstances. Many States have extended the

length of time for which a complaint can

be filed, other States have eliminated

statutes of limitation for certain crimes,

and some legislation is retroactive. 

Exceptions to statutes. Exceptions often

exist under existing and new statutes.

Under such exceptions, time can be

added to the statute of limitation, giving

police the legal authority to arrest even if

it appears as though the statute has run

out. For example, many jurisdictions have

exceptions for a suspect’s flight from jurisdiction. In a case for which there is a 

5-year statute of limitation, if the government can prove that the suspect has been

absent from the jurisdiction for 2 years,

the State can still file against the suspect

for up to 7 years after the commission of

the crime. Exceptions also exist for cases

in which child victims are assaulted by a

family member, which can be valuable in

the context of a current investigation.

Victim and witness 

considerations

Another important consideration to be

made early in the process is the willingness of victims and witnesses to proceed.

Although many victims may continuously

monitor the progress of their investigations, some choose to detach from the

process over time. Reinvestigating a case

may cause renewed psychological trauma

to the victim and victim’s family. It should

not be assumed that victims and witnesses, even if they were eager to pursue the

case when it occurred, are still interested

in pursuing the case. A phone call from an

investigator years later may not be a welcome event. Whenever possible, enlist

the aid of victim service providers. If a

new officer is handling the investigation,

enlisting the assistance of the original

investigator to make the first contact with

the victim may also be helpful. 

The older a case is, the more difficult it

may be to locate witnesses. However,

early identification of victim and witness

availability may ultimately save significant

resources. Consultation with prosecutors

is mandatory when considering whether a

witness would be necessary at trial.

15

USING DNA TO SOLVE COLD CASES

STATUTE OF LIMITATION RECOMMENDATIONS

■ Know the original statute of limitation.

■ Determine whether the law has changed regarding time limits for filing. 

If so, is the law retroactive?

■ Determine whether there are exceptions to the statute.

■ Consult with the prosecutor.

It should not be

assumed that

victims and witnesses are still

interested in pursuing the case.

Whenever possible, enlist the

aid of victim

service providers.
17

Whether the process of reviewing

unsolved cases is initiated by a single officer or by a specialized unit, it must ultimately be a team effort. At all stages of

the process, investigators should avail

themselves of the scientific advice of the

laboratory and the legal expertise of the

local prosecutor’s office. Close consultation with the laboratory can ensure that

evidence integrity is maintained and that

limited laboratory resources are allocated

effectively. Similarly, prosecutors can help

identify issues that might occur at trial if a

suspect is identified and arrested upon

successful DNA testing. Good communication between police, laboratories, and

prosecutors can help identify and convict

serious offenders and save valuable time

and resources. 

Identify potential cases

for review

An initial step in the DNA review of

unsolved cases is to identify cases that

might be amenable to DNA testing. While

the cases considered for this kind of

review will vary from jurisdiction to jurisdiction, it is important to define minimum

requirements that will likely benefit from

this approach. Issues such as statutes of

limitation and solvability factors should be

thoroughly examined in cooperation with a

prosecutor and the forensic laboratory to

establish guidelines for case selection. It

also will be important to identify the ultimate goals of the program so that the

selection criteria can be tailored to meet

those specific goals. 

Cases that could benefit from a review

for potential DNA evidence can be identified from numerous sources. In some

instances a single police officer or investigator may remember an unsolved case

from years ago. In some departments a

formalized cold-case unit may systematically review cases for the potential of DNA

testing. Other cases may be identified by

coordinated, interdepartmental efforts, victims or witnesses who have heard about

the potential of DNA evidence, and laboratories taking inventory of their storage

facilities. If a department is pursuing a systematic review of cases, either by one or

two officers or by a formal unit, there are

many sources that can be consulted for

valuable investigative information, such

as—

■ Autopsy, laboratory, prosecutor, and

local agency logbooks.

■ Retired investigators.

■ Computer databases.

Identify statute of

limitation issues

Statute of limitation issues might affect

the ultimate ability to prosecute a case.

Cases should be preliminarily reviewed by

investigators in conjunction with the prosecutor’s office to identify which prosecutions would be barred by the statutes of

limitation. If the goal of the unsolved case

review program is to obtain convictions

and statutes of limitation have expired on

a particular case, a department may wish

to save its resources for cases likely to

yield convictions. However, if the goal

of the program is to solve and close unsolved cases regardless of whether a conviction could be obtained, a jurisdiction

may decide to review all cases that qualify

under its guidelines. This is an important

consideration in the context of investigating serial offenders whose criminal acts

might span the course of years or

decades.

Identifying, Analyzing, and 

Prioritizing Cases

Good

communication

between police,

laboratories, and

prosecutors can

help identify and

convict serious

offenders and save

valuable time

and resources.
18

SPECIAL REPORT / JULY 02

Define categories of cases—

solvability factors

Because the number of cases that qualify

for reinvestigation might be very large, it

may be beneficial for a jurisdiction to

define cases according to several solvability factors. Solvability factors include facts

and circumstances of a case that influence

the likelihood that it might be solved

through advancements in DNA technology. For example, a high probability exists

that analysis of nonsuspect rape kits will

yield valuable DNA results. Profiles generated as a result of DNA analysis can now

be entered into CODIS, which can solve a

case by matching to a convicted offender,

or aid investigations by linking serial rapes

to each other. Additionally, if an unsolved

murder case contains biological evidence

foreign to the victim that did not produce

viable results from ABO blood typing or

RFLP DNA analysis, evidence could be

reanalyzed with the more discriminating

and powerful STR technology. It is also

important to recognize and sort out cases

that might not be as likely to be solved

with DNA technology. An example might

be an unsolved drive-by homicide because

the perpetrator most likely would not have

left biological evidence at this kind of

crime scene.

Case review—

establish priorities

Once solvability factors and statute of limitation issues are addressed, it is important

to continue the process by identifying the

cases to be reviewed first. To preserve

investigative resources when considering

a larger number of unsolved cases for

review, jurisdictions may prioritize according to the likelihood that cases will be

solved or the likelihood that investigations

will be aided. In establishing this priority,

the following criteria can be considered:

■ How many qualifying cases are there? ■ Where are the case files located? ■ Are case summaries available? ■ How many cases will be assigned to

an investigator?

To establish an investigative hierarchy,

qualifying cases should be reviewed by

experienced, proficient investigators. A

checklist can be used throughout the

review process so that managers can

decide which cases will be worked first. A checklist can also provide review process consistency throughout the agency.

(See Sample Checklist at the end of this

report.) The following categories may

serve as a model for a hierarchy in prioritizing cases: ■ There is a known suspect and physical

evidence appears to have been preserved in a manner consistent with successful DNA testing and use of CODIS.

■ There is no known suspect but physical

evidence has been preserved in a manner consistent with successful DNA

testing and use of CODIS.

■ There is no known suspect and evidence was collected and preserved in a manner that may make it difficult to

obtain a DNA profile. 

Locating case files, 

obtaining evidence logs,

and other documentation

Locating the case file and original evidence

for the investigation may be a challenging

endeavor. Changes in personnel, procedure, and facilities and the passage of

time may complicate the process. When

searching for a case file or evidence, an

investigator may need to look in numerous
19

USING DNA TO SOLVE COLD CASES

places. Potential locations include, but are

not limited to, the following:

■ Police department property rooms (case

files, evidence logs, whole evidence).

■ Property warehouses (case files, evidence logs, whole evidence).

■ Public crime laboratories (previously

tested/submitted evidence, lab reports).

■ Private laboratories (previously tested

evidence, lab reports).

■ Hospital/medical facilities (rape kits,

medical reports, slides).

■ Coroner/medical examiners’ offices

(autopsy reports).

■ Courthouse property rooms.

■ Prosecutors’ offices (previous trial or

suspect investigation).

■ Retired investigators’ files (case notes

and details not contained in file).

■ Other investigating agency offices

(investigative leads—serial offender).

Forensic testing reports and 

previously tested evidence

Because advancements in DNA technology enable laboratories to successfully analyze old evidence that might have been

improperly stored or subjected to previous

forensic analysis, it will be very valuable to

locate any and all forensic reports that

were produced as a result of previous

analysis and/or testing. ABO blood typing,

microscopic hair analysis, RFLP DNA

analysis, or fingerprint analysis (among

others) might have been performed in the

course of the original investigation. The

original case file should indicate whether

and which types of forensic analysis were

attempted. These reports also serve to

memorialize proper chain of custody.

Cooperation with the crime laboratory is

crucial to locate and interpret existing

forensic reports and to determine whether

evidence would be amenable to reanalysis

with new DNA techniques. 

Many combinations of options are available to investigators and laboratory personnel if biological evidence was available

and previously tested. Exhibit 3 may serve

to help investigators as they work with the

laboratory to discuss options throughout

the course of the investigation.

Locate biological evidence

When reviewing the case file for potential

DNA evidence, it is important to know

what kinds of evidence may yield a DNA

profile. Given the power and sensitivity of

newer DNA testing techniques, DNA can

be collected from virtually anywhere. Only

a few cells can be sufficient to obtain useful DNA information to help solve a case.

Exhibit 4 identifies some common items of

evidence that may have been collected previously but not analyzed for the presence

of DNA evidence. Remember, if a stain is

not visible it does not mean that there are

not enough cells for DNA typing. Further,

DNA does more than just identify the

source of the sample; it can place a known

individual at a crime scene, in a home, or in

a room where the suspect claimed not to

have been. It can refute a claim of selfdefense and put a weapon in the suspect’s

DNA CAN DO MORE . . . 

. . . than identify a suspect. It can also—

■ Place a known individual at a crime scene.

■ Refute a claim of self-defense.

■ Put a weapon in a suspect’s hand.

■ Change a suspect’s story from an alibi to one of consent.
20

SPECIAL REPORT / JULY 02

hand. It can also provide irrefutable evidence that can change a suspect’s story

from an alibi to one of consent. 

Evaluate for probative

DNA evidence

On completion of reviewing the case file,

reports, and evidence in consultation with

the laboratory, it will be necessary to identify which evidentiary items will be

amenable to DNA analysis. Consultation

with the laboratory will be essential to

determine the likelihood of obtaining

results from DNA analysis, and consultation with a prosecutor is very important to

determine which evidence will be probative to the case. Building the new investigation on cooperative efforts between the

laboratory and prosecutor can save valuable resources, develop leads, and identify

previously overlooked evidence that may

yield a DNA profile.

Continue investigative 

protocol

If DNA analysis is to be conducted, it may

be important to obtain reference samples

from prior suspects, and it might be necessary to be creative when obtaining

these samples. While a biological sample

in the form of blood or saliva can be

obtained voluntarily through a consent

form, a standard reference sample might

already exist if previous forensic analysis,

Exhibit 3. Investigative options

Test conducted Original results Original interpretation Options for investigators

RFLP/PCR Obtained profiles. No suspects identified. Is the original extract remaining?

1. If so, retest using STR technique and 

submit to CODIS.

2. If not, reextract the original sample 

using STR technique and submit to 

CODIS.

RFLP Inconclusive or no results obtained. Sample size may have been Is the original extract remaining?

insufficient or not concentrated 1. If so, retest using STR technique and

enough. submit to CODIS.

2. If not, reextract the original sample 

using STR technique and submit to 

CODIS.

PCR Inconclusive or result intensity Sample size may have been Is the original extract remaining?

below “S” and “C” dots. insufficient. 1. If so, retest using STR technique and

submit to CODIS.

2. If not, reextract the original sample

using STR technique and submit to 

CODIS.

Conventional serology (ABO, secretor Obtained a type in these systems. Poor statistics and no searching If original evidence still exists, extract 

status, enzymes such as EsD, PGM, capability. the sample using STR technique and

GLO I, EAP, ADA, AK). submit to CODIS.

None 1. Limited sample size. If original evidence still exists, extract 

2. No suspects, did not process the sample using STR technique and

further. submit to CODIS.

3. No request at the time of

analysis.
21

USING DNA TO SOLVE COLD CASES

Exhibit 4. Common items of evidence

Evidence Possible location of DNA on the evidence Source of DNA

Baseball bat Handle Skin cells, sweat, blood, tissue

Hat, bandanna, or mask Inside surfaces Sweat, hair, skin cells, dandruff, saliva

Eyeglasses Nose or ear piece, lens Sweat, skin cells

Facial tissue, cotton swab Surface Mucus, blood, sweat, semen, ear wax

Dirty laundry Surface Blood, sweat, semen, saliva

Toothpick Surface Saliva

Used cigarette Cigarette butt (filter area) Saliva

Used stamp/envelope seal Moistened area Saliva

Tape or ligature Inside or outside surface Skin cells, sweat, saliva

Bottle, can, or glass Mouthpiece, rim, outer surface Saliva, sweat, skin cells

Used condom Inside/outside surface Semen, vaginal or rectal cells

Bed linens Surface Sweat, hair, semen, saliva, blood

“Through and through” bullet Outside surface Blood, tissue

Bite mark Surface of skin Saliva

Fingernail/partial fingernail Scrapings Blood, sweat, tissue, skin cells

Note: When reviewing evidence, it is important to maintain chain of custody, consult with laboratory personnel, and take all appropriate precautions against contamination,

including wearing gloves and changing them between handling of different pieces of evidence. 

such as serological testing, was performed during the course of the original

investigation.

Additionally, elimination samples from anyone who had lawful access to the crime

scene, such as family members, may be

required if the laboratory determines that

there is more than one DNA profile present in the evidence sample. Early identification of the location and status of

persons who might be requested to submit an elimination sample could save valuable time and resources if the laboratory

needs such information. Consultation with

the laboratory is essential to properly coordinating this process.

Follow agency procedures

for submitting the DNA 

profile to CODIS

On successful laboratory analysis resulting

in a DNA profile developed from crime

scene evidence, existing and/or new suspect DNA profiles should be compared

with the evidence profile. If the laboratory

determines a match between a suspect

and the evidence, the prosecutor’s office

should be consulted on how to proceed.

However, if a match is not found, agency

procedures should be followed, in accordance with the crime laboratory, to submit

the crime scene evidence DNA profile into

CODIS. 
22

SPECIAL REPORT / JULY 02

Because CODIS contains hundreds of

thousands of convicted offender DNA profiles, it is possible that the person who

committed the unsolved crime being

investigated was convicted of a qualifying

offense that required submission of a

DNA profile to the database. If that person

has not previously been convicted of a

qualifying offense, especially in light of

expanding database law, it is possible that

they will be convicted in the future.

Further, because the forensic index of

CODIS contains thousands of crime scene

evidence profiles, the investigation could

be aided if a match is made to another

forensic DNA profile already in the database. Finally, an investigator should not

assume that a new DNA profile generated

from unsolved case evidence and submitted to the laboratory for entry into CODIS

will be compared with every possible convicted offender or crime scene index profile. The investigator may need to

proactively request that his CODIS administrator search the new profile against the

local, State, and national DNA databases.

Prepare a John Doe warrant

CODIS is a powerful crime-solving and

crime-prevention tool, but many cases will

not be solved as a result of entering a

DNA profile into the forensic index of the

database. Additionally, many cases will

have statute of limitation issues that might

prevent the prosecution of the case if a

match is not determined in a timely manner. Therefore, if no offender match

occurs in cases in which statutes of limitation are an issue, consideration may be

given, in consultation with the prosecutor,

to preparing a John Doe warrant. These

types of warrants can identify the perpetrator according to his or her DNA profile.

The 13-loci profile generated by the crime

laboratory should be clearly printed on the

face of the warrant. The John Doe warrant

is not novel; however, the unconventional

method of describing an individual by his

or her DNA profile may allow for prosecution of a case if a DNA match is 

determined in the course of future investigations or as a result of the CODIS system being populated with more convicted

offender and forensic DNA profiles.

Notes

1. CODIS uses two indexes—the forensic index and

the offender index—to generate investigative leads

in crimes where biological evidence is recovered

from crime scenes. The forensic index contains DNA

profiles of biological crime scene evidence and the

offender index contains DNA profiles of individuals

convicted of a qualifying offense.

2. CODIS has a missing persons index that exclusively contains mtDNA profiles; the convicted offender

and forensic indexes of CODIS exclusively contain

STR DNA profiles.
23

USING DNA TO SOLVE COLD CASES

SAMPLE CHECKLIST

■ Identify potential cases.

■ Identify any statute of limitation issues (consult with prosecutors).

■ Define case categories according to solvability factors.

■ Prioritize cases (consider solvability factors).

■ Locate and review the case file; obtain evidence logs and other documentation 

such as laboratory and autopsy reports.

■ Locate previous forensic testing reports and location of previously tested evidence. 

For example—

■ Blood previously ABO typed.

■ Hair analyzed microscopically.

■ Fingerprint evidence.

■ Locate crime scene evidence containing biological material.

■ Evaluate the case and evidence for potential probative DNA. Be sure to—

■ Consider all evidentiary possibilities.

■ Take appropriate precautions against contamination.

■ In consultation with the laboratory and prosecutors, submit appropriate (probative) 

evidence to the laboratory for testing.

■ Continue investigative protocol. If needed, obtain reference samples from suspects—

■ Voluntarily using a consent form. ■ By using a previously obtained sample (e.g., if a reference sample was used 

for standard serological testing). 

■ Identify witness issues—

■ Legal availability.

■ Willingness to proceed.

■ Location.

■ If a profile does not match suspect profiles, follow agency procedures for submitting the 

evidence profile to CODIS.

■ If no offender match occurs in cases in which statutes of limitation are an issue, prepare 

a John Doe warrant. 
About the National Institute of Justice

NIJ is the research, development, and evaluation agency of the U.S. Department of Justice and

is solely dedicated to researching crime control and justice issues. NIJ provides objective, independent, nonpartisan, evidence-based knowledge and tools to meet the challenges of crime and

justice, particularly at the State and local levels. NIJ’s principal authorities are derived from the

Omnibus Crime Control and Safe Streets Act of 1968, as amended (42 U.S.C. §§ 3721–3722).

NIJ’s Mission

In partnership with others, NIJ’s mission is to prevent and reduce crime, improve law enforcement

and the administration of justice, and promote public safety. By applying the disciplines of the

social and physical sciences, NIJ—

• Researches the nature and impact of crime and delinquency.

• Develops applied technologies, standards, and tools for criminal justice practitioners.

• Evaluates existing programs and responses to crime.

• Tests innovative concepts and program models in the field.

• Assists policymakers, program partners, and justice agencies.

• Disseminates knowledge to many audiences.

NIJ’s Strategic Direction and Program Areas

NIJ is committed to five challenges as part of its strategic plan: 1) rethinking justice and the

processes that create just communities; 2) understanding the nexus between social conditions

and crime; 3) breaking the cycle of crime by testing research-based interventions; 4) creating the

tools and technologies that meet the needs of practitioners; and 5) expanding horizons through

interdisciplinary and international perspectives. In addressing these strategic challenges, the

Institute is involved in the following program areas: crime control and prevention, drugs and

crime, justice systems and offender behavior, violence and victimization, communications and

information technologies, critical incident response, investigative and forensic sciences (including DNA), less-than-lethal technologies, officer protection, education and training technologies,

testing and standards, technology assistance to law enforcement and corrections agencies, field

testing of promising programs, and international crime control. NIJ communicates its findings

through conferences and print and electronic media.

NIJ’s Structure

The NIJ Director is appointed by the President and confirmed by the Senate. The NIJ Director

establishes the Institute’s objectives, guided by the priorities of the Office of Justice Programs,

the U.S. Department of Justice, and the needs of the field. NIJ actively solicits the views of criminal justice and other professionals and researchers to inform its search for the knowledge and

tools to guide policy and practice.

NIJ has three operating units. The Office of Research and Evaluation manages social science

research and evaluation and crime mapping research. The Office of Science and Technology

manages technology research and development, standards development, and technology assistance to State and local law enforcement and corrections agencies. The Office of Development

and Communications manages field tests of model programs, international research, and knowledge dissemination programs. NIJ is a component of the Office of Justice Programs, which also

includes the Bureau of Justice Assistance, the Bureau of Justice Statistics, the Office of Juvenile

Justice and Delinquency Prevention, and the Office for Victims of Crime. 

To find out more about the National

Institute of Justice, please contact:

National Criminal Justice 

Reference Service

P.O. Box 6000

Rockville, MD 20849–6000

800–851–3420

e-mail: askncjrs@ncjrs.org
U.S. Department of Justice

Office of Justice Programs

National Institute of Justice

Washington, DC 20531

Official Business

Penalty for Private Use $300

JULY 02

NCJ 194197