Guiding Principles for Scene Investigation and Reconstruction

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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
Guiding Principles for Scene Investigation and Reconstruction

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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: 2.0

September 2021

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.
Guiding Principles for Scene Investigation and Reconstruction

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Foreword

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

reconstructionists a baseline for the guiding principles for scene 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.

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

validity, reconstructionist, scene investigation 

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.
Guiding Principles for Scene Investigation and Reconstruction

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Table of Contents

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

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

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

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

4.1 Legal Considerations..................................................................................... 7

4.2 Personnel Safety....................................................................................... 7

4.3 Scientific Reliability and Validity........................................................................ 7

4.4 Preserving Context ....................................................................................... 7

4.5 Maintaining Evidence Integrity ......................................................................... 8

4.6 Transparency and Ethics................................................................................... 8

4.7 Managing Bias.............................................................................................. 8

5 Annex A (informative) Bibliography.....................................................................10
Guiding Principles for Scene Investigation and Reconstruction

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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

CSR 

A scene reconstruction that involves a potential criminal act.

3.5

crime scene reconstructionist

CSR

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

reconstruction that involves a potential criminal act.

3.6

scene

A place or object that is subject to and/or requires forensic examination. (ISO/FDIS 21043-
Guiding Principles for Scene Investigation and Reconstruction

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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 is safe and best preserves the evidence and its context. The scene 

investigator should 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

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. 
Guiding Principles for Scene Investigation and Reconstruction

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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, peerreviewed studies, and/or validated techniques prior to use on scenes. 

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. 

1

https://www.nist.gov/osac/osac-registry
Guiding Principles for Scene Investigation and Reconstruction

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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.

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.
Guiding Principles for Scene Investigation and Reconstruction

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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).
Guiding Principles for Scene Investigation and Reconstruction

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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/attachmen

t_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.

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

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

Forensic Sci., 34(3), 719–729, 1989.

6] 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

7] 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.

8] 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