OSAC 2021‐N‐0015

Guiding Principles for Scene

Investigation and

Reconstruction

Crime Scene Investigation & Reconstruction Subcommittee

Scene Investigation Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
OSAC 2021‐N‐0015

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OSAC Proposed Standard

OSAC 2021‐N‐0015

Guiding Principles for Scene

Investigation and Reconstruction

Prepared by  

Crime Scene Investigation & Reconstruction Subcommittee

Version: 2.1

January 2024

Disclaimer:

This OSAC Proposed Standard was written by the Crime Scene Investigation & Reconstruction

Subcommittee of the Organization of Scientific Area Committees (OSAC) for Forensic Science

following a process that includes an open comment period. This Proposed Standard will be

submitted to a standards developing organization and is subject to change. There may be

references in an OSAC Proposed Standard to other publications under development by OSAC.

The information in the Proposed Standard, and underlying concepts and methodologies, may be

used by the forensic‐science community before the completion of such companion publications.

Any identification of commercial equipment, instruments, or materials in the Proposed Standard

is not a recommendation or endorsement by the U.S. Government and does not imply that the

equipment, instruments, or materials are necessarily the best available for the purpose.

Version

No.

Issue Date Section Reason

2.0 September 7, 2021  ‐‐  Added to the OSAC Registry and publicly announced.

2.1 January 8, 2024 All Format and font updates only. No content changes made.
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Foreword

This standard was developed to provide guidance to scene investigators and scene

reconstructionists a baseline for the guiding principlesforscene investigation and reconstruction.

This document has been prepared by the Organization of Scientific Area Committees (OSAC) for

Forensic Science Crime Scene Investigation and Reconstruction Subcommittee.

Abstract: This document provides minimum standards and recommendations for practicing

scene investigation and reconstruction. This document provides guiding principles for the

identification, documentation, collection, preservation of physical evidence, and scene

reconstruction.

Keywords: crime scene, reconstruction, chain of custody, ethics, bias, safety, contamination,

validity, reconstructionist, scene investigation   
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Table of Contents

1 Scope .....................................................................................................................................5

2 Normative References........................................................................................................... 5

3 Terms and Definitions............................................................................................................ 5

4 Guiding Principles.................................................................................................................. 6

Annex A.......................................................................................................................................10
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Guiding Principles for Scene Investigation and Reconstruction

1 Scope

This standard describes the minimum general standards of practice or guiding principles for

practicing scene investigators and reconstructionists. These Guiding Principles establish a

framework for expected behavior and for decision‐making. These principles include legal

considerations, personnel safety, scientific reliability and validity, preserving context,

maintaining evidence integrity, transparency and ethics, and managing bias.

2 Normative References

There are no normative documents.  

3 Terms and Definitions

For purposes of this document, the following definitions and acronyms apply.  

3.1

cognitive bias

A set of influences that may affect the reliability and validity of one’s observations and

conclusions. [OSAC Preferred Terms]

3.2

crime scene investigation  

CSI

A scene investigation that involves a potential criminal act.

3.3

crime scene investigator

CSI

An individual, however named, who is responsible for performing elements of a scene

investigation that involves a potential criminal act.

3.4

crime scene reconstruction

A scene reconstruction that involves a potential criminal act.

3.5

crime scene reconstructionist

An individual, however named, who is responsible for performing elements of a scene

reconstruction that involves a potential criminal act.
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3.6

scene

A place or object that is subject to and/or requires forensic examination. (ISO/FDIS 21043‐ 

1:2018[E])  

NOTE A crime scene is a common description of a scene where a presumed crime has been

committed. The scene can be a person or an animal.

3.7

scene investigation

An examination of a scene to locate, document, collect, and preserve items of potential

evidentiary value.

3.8

scene investigator

An individual, however named, who is responsible for performing elements of scene

investigation.

3.9

scene reconstruction

The utilization of information gathered from the investigative process to develop or eliminate

possible explanations for how an incident occurred.

3.10

scene reconstructionist

An individual, however named, who is responsible for performing elements of scene

reconstruction.

4 Guiding Principles

The goal of scene investigation is to provide information that will help criminal investigators,

lawyers, and triers‐of‐fact ascertain what happened at a scene. The scene investigator endeavors

to locate, document, collect and preserve all items of potential evidentiary value. Each scene is

unique and requires scene investigators and reconstructionists to continuously evaluate how to

proceed with processing in a manner that issafe and best preservesthe evidence and its context.

The scene investigatorshould take care to consider alternative hypotheses about what may have

occurred, and proceed in a manner that is safe and that best preserves the evidence and context

relevant to all plausible hypotheses. Thus, all decisions made by a scene investigator or

reconstructionist before, during, and after a scene is processed should consider the following:

1. Legal considerations

2. Personnel safety

3. Scientific reliability and validity

4. Preserving context

5. Maintaining evidence integrity
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6. Transparency and ethics

7. Managing cognitive bias

Scene investigation and reconstruction are led by general guiding principles. Though all the

guiding principles listed in this document are important, some circumstances could require a

scene investigator or reconstructionist to give greater weight to one principle over another. A

decision to deviate from a guiding principle shall be documented and explained.

4.1 Legal Considerations

Scene investigators and reconstructionists shall conduct themselves with the expectation that

their work may be used in every step of the legal process, and therefore shall ensure that they

comply with applicable legal standards including those of search and seizure.

4.2 Personnel Safety

Scenes can present a wide variety of physical, biological, chemical, and situational hazards with

a level of personal risk of injury, illness, or exposure almost always present. Personnel shall not

be exposed to an unreasonable level of risk to personal safety and shall be provided with the

equipment and training necessary to mitigate risks.

a) Scene investigators and reconstructionists shall have appropriate personal protective

equipment (PPE) to mitigate hazards presented by the scene and by any processing tools,

equipment, or reagents used.

b) Scene investigators and reconstructionists shall be trained in the proper use of PPE. Some

forms of PPE may require fit testing or certification for safe use.

c) PPE protocols shall include:

i. Hazard assessment and PPE selection.

ii. PPE cleaning, maintenance, decontamination, and storage.

d) PPE considerations should include, but not limited to, protection of eyes and face, head,

foot and leg, hand and arm, body (torso), respiratory system, and hearing; and protection

against, falls, and drowning.

4.3 Scientific Reliability and Validity

Scene investigators and reconstructionists shall use scientifically reliable and valid methods,

practices, and analytical procedures.

a) Methods, practices and analytical procedures shall be based on best practices, peer‐

reviewed studies, and/or validated techniques prior to use on scenes.
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b) When applicable, methods, practices and analytical procedures published in the OSAC

Registry shall be employed.1

4.4 Preserving Context

Scene investigators and reconstructionists shall document a scene in such a way that it preserves

the context of the evidence to ensure others can later understand not just what was collected,

but also where, how, and in what condition it was found.

4.5 Maintaining Evidence Integrity

Scene investigators and reconstructionists shall take appropriate steps to maintain evidence

integrity by preventing contamination, tampering, alteration, or loss of evidence. Procedures and

documents shall be utilized to account for the integrity and possession of evidence by tracking

its handling and storage from its point of collection to its final disposition.

4.6 Transparency and Ethics

The work of a scene investigator and reconstructionist generates the underlying basis for all

subsequent analysis of the scene. The scene investigator and reconstructionist shall provide

documentation and testimony of the scene that clearly represents its initial condition, their

actions on‐scene, and any other relevant factors.

a) If an action by an investigator will intentionally deviate from, or set aside, one of the

principles, the circumstances and justification shall be fully documented.

b) Upon discovery of unintentional deviations, errors, omissions, or acts of nonconformance

with the principles, the circumstances shall be fully documented and explained.

c) While an enumerated Code of Ethics is beyond the scope of this standard, scene

investigators and reconstructionists have professional duties that they are bound to and

shall execute. These include, but are not limited to, the duty to:

i. remain competent in a wide range of scientific fields.

ii. be as objective as reasonably possible.

iii. act thoroughly and to produce results, conclusions, and testimony within the

scope of the expertise of the individual practitioner.

4.7 Managing Cognitive Bias

Scene investigators and reconstructionists are uniquely positioned at the intersection of law

enforcement and scientific investigations, and shall ascertain the facts, without regard to

potentially biasing influences.

1

 https://www.nist.gov/osac/osac‐registry 
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a) Scene investigators and reconstructionists shall take steps to mitigate effects of cognitive

biases on their work.

b) In order to identify all relevant evidence, the scene investigator must consider various

possible hypotheses about what happened and should endeavor to locate, document,

collect, and preserve evidence relevant to all plausible hypotheses.   The scene

investigator must take care not to fixate too quickly on a particular hypothesis, as the

tendency to prematurely adopt a theory of the case, and then seek confirmation for that

theory, is a form of cognitive bias that can cause investigators to miss, ignore, or discount

important evidence.  When searching for relevant evidence, the crime scene investigator

should consider both evidence that may support various hypotheses as well as evidence

that might undermine or contradict those hypotheses. Both the presence and the absence

of such items and traces should be documented and noted.

c) A scene may be full of potentially biasing influences. Decisions made by scene

investigators and reconstructionists depend on and require some contextual information

and hypothesis formulation, which guide them in their search for evidence and/or

analysis. It is critical that hypotheses are well‐determined, as they can lead to

identification and collection of important evidence or, alternatively, mislead the

investigator.

d) As with forensic laboratory analysis, the scene investigator and reconstructionist shall

remain as independent as possible from non‐scene‐related and potentially biasing case

information (e.g., suspect or victim criminal history).

   
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Annex A

(informative)

Bibliography

1] Bowen, Robin. Ethics and the Practice of Forensic Science. 2nd Ed. CRC Press, 2018.

2] Dror, Itiel E. Cognitive neuroscience in forensic science: understanding and utilizing the

human element 370 Phil. Trans. R. Soc. B http://doi.org/10.1098/rstb.2014.0255, August

2015.

3] Forensic Science Regulator Guidance.  Cognitive Bias Effects Relevant to Forensic Science

Examinations.  FSR‐G‐217 Issue 2  Crown Copyright 2020.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment

_data/file/914259/217_FSR‐G‐217_Cognitive_bias_appendix_Issue_2.pdf

4] Houck, Max and Siegel, Jay. Fundamentals of Forensic Science. Elsevier Academic Press,

2006.

5] ISO 21043‐1:2018(E) Forensic sciences‐ Part 1: Terms and definitions.

6] Lucas, D. The ethical responsibilities of the forensic scientist: Exploring the limits, J. Forensic

Sci., 34(3), 719–729, 1989.  

7] National Forensic Science Technology Center. Crime Scene Investigation: A Guide for Law

Enforcement [supported under cooperative agreements by BJA, NIJ, and NIST]. NFSTC,

2013.2

8] U.S. Department of Labor Occupational Safety and Health Administration. Personal

Protective Equipment [OSHA Publication 3151‐12R],

https://www.osha.gov/Publications/osha3151.pdf, 2004.

9] United States Department of Labor, Occupational Health and Safety Administration.

Standard 1910 Subpart I Personal Protective Equipment [Occupational Health and Safety

Standards]3

2 Available free at https://www.nist.gov/sites/default/files/documents/forensics/Crime‐Scene‐Investigation.pdf 3 Available at https://www.osha.gov/laws‐regs/regulations/standardnumber/1910