Standard for Initial Response at Scenes by Law Enforcement

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OSAC 2021-N-0016 

Standard for Initial 

Response at Scenes by Law 

Enforcement

Crime Scene Investigation & Reconstruction Subcommittee

Scene Examination Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
Standard for Initial Response at Scenes by Law Enforcement

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OSAC Proposed Standard

OSAC 2021-N-0016 

Standard for Initial Response at Scenes 

by Law Enforcement

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.
Standard for Initial Response at Scenes by Law Enforcement

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Foreword

This standard specifies best practices to be employed by law enforcement officers (LEO) 

when they arrive at an incident which could be expected to become the subject of criminal or 

civil litigation. This standard applies to instances where the responding person’s primary 

responsibility is initial response and securing the scene and not scene examination and 

evidence collection. In instances where the responding LEO is also responsible for scene 

examination, documentation, and evidence recovery, they should refer to applicable 

additional standards. This document recommends generally accepted professional principles 

and practices. The details and issues of each situation and scene require consideration and 

will dictate the course of actions to be undertaken by the LEO. Deviations from this standard 

should be based on specific articulable circumstances. This standard cannot replace 

knowledge, skill, or ability acquired through appropriate education, training, and experience 

and should be used in conjunction with sound professional judgement. This standard 

provides guidance on some safety issues but is not exhaustive. It is the responsibility of the 

appropriate agency to develop a full health and safety plan. 

This standard is not intended to make agency-specific protocols. This document is intended 

to inform individual agency protocols dictating how LEOs are to respond to, approach, and 

enter a scene with a focus on evidence integrity and consideration for safety, security, and 

medical intervention. This document is intended to provide investigators with a safer work 

environment and to limit alterations to a scene, witnesses, persons of interest, and evidence 

so that all aspects of the scene are in a substantially similar condition as they were found 

when law enforcement initially encountered them. 

Keywords: Crime scene, document, examination, law enforcement, response, investigation
Standard for Initial Response at Scenes by Law Enforcement

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Table of Contents

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

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

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

4 Requirements............................................................................................................................6

4.1 Overview.....................................................................................................................................6

4.2 Arrival Procedure........................................................................................................................6

4.3 Safety Considerations.................................................................................................................7

4.4 Medical Intervention.................................................................................................................7

4.5 Assessing the Scene.....................................................................................................................7

4.6 Scene Containment and Control..................................................................................................7

4.7 Evidence Preservation.................................................................................................................8

4.8 Turning a Scene Over to Investigators........................................................................................8

4.9 Recording Scene Conditions........................................................................................................8

Annex A (informative) Bibliography...................................................................................................10

Standard for Initial Response at Scenes by Law Enforcement

1 Scope

This standard describes the protocols required for the initial response by law enforcement to scenes. 

These protocols include: arrival procedure, safety considerations, medical intervention, assessing 

the scene, scene containment and control, evidence preservation, turning the scene over to 

investigators, and document actions and observations. It does not include protocols for a complete 

scene investigation.

2 Normative References

Guiding Principles for Scene Investigation and Reconstruction [OSAC Proposed Standard]

Standard Practice for Crime Scene Investigator Training, Continuing Education, Professional 

Development, Certification, and Accreditation [OSAC Proposed Standard]

3 Terms and Definitions

For purposes of this document, the following definitions apply.

3.1 

crime scene investigation

CSI
Standard for Initial Response at Scenes by Law Enforcement

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A scene investigation that involves a potential criminal act.

3.2

crime scene investigator

CSI

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

involves a potential criminal act.

3.3

crime scene preservation

See scene preservation.

3.4

contamination 

The undesirable introduction of a substance to an item at any point in the forensic process. Note: This 

includes undesirable transfer of a substance within an item or between items, also referred to as 

cross-contamination. (ISO 21043-1)

3.5

law enforcement officer (LEO)

Any public employee whose duties primarily involve enforcement or investigation of laws. 

3.6

personal protection equipment (PPE)

Equipment worn to minimize exposure to a variety of hazards such as body-fluids, irritants, or 

contaminants. Examples of PPE: gloves, foot and eye protection, respirators, and full body suits.

3.8

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. 

3.9

scene investigation

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

[Guiding Principles]

3.10

scene investigator

An individual, however named, who is responsible for performing elements of scene investigation. [Guiding 

Principles]

3.11

scene preservation

The intentional act of refraining from any activity that may alter a scene or anything contained within 

the scene. [Guiding Principles]

4 Requirements
Standard for Initial Response at Scenes by Law Enforcement

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4.1 Overview

4.1.1 Every scene has the potential to yield evidence that may aid in a criminal 

investigation. As such, the first responding LEO to a scene shall take all reasonable actions to 

preserve the scene in order to maintain evidence integrity until a designated scene

investigator (CSI) is able to respond.

4.1.2 Scene investigation is the responsibility of the responding officer in some jurisdictions 

while in others a dedicated unit is deployed to a scene and the responding officer passes the 

management of the scene to CSI personnel upon arrival. In such instances, an exchange of 

information shall take place between the officer and the CSI personnel. 

 

4.1.3 There are some instances where alteration to the scene prior to CSI response cannot be 

avoided, including actions for safety and security, or during medical intervention. Any actions 

taken and any known changes to the scene shall be documented and relayed to those responsible 

for the investigation. 

4.2 Arrival Procedure

4.2.1 Upon arrival of the first responding LEO(s) to a scene, after reasonably assessing and 

addressing any threats or risks of harm to prevent additional injuries or loss of life to the public and 

other responders, shall:

a) assume the scene is a crime scene, until determined otherwise.

b) make initial observations.

c) make a reasonable attempt to document the identity and contact information of any 

person(s) at or leaving the scene.

d) make a reasonable attempt to document any vehicles leaving the scene.

4.3 Safety Considerations

4.3.1 LEO(s) shall take reasonable precautions to ensure the safety of all parties, while 

minimizing changes to the scene. Mitigating actions should include, but are not limited to: 

a) leaving adequate space for ingress/egress for additional emergency response, should 

additional emergencies arise.

b) contacting appropriate personnel/agencies if hazards such as chemical, radiological, gas, 

biological, animal, physical, or electrical are suspected or discovered.

c) directing additional responding units and personnel to minimize any impact to the scene.

d) wearing personal protective equipment (PPE) at all times.

e) moving a weapon only when necessary to eliminate the threat of harm.

4.4 Medical Intervention
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4.4.1 The initial responding officer(s) shall ensure that medical attention is provided with 

minimal contamination of the scene and that appropriate PPE is worn while providing medical 

attention.

4.5 Assessing the Scene

4.5.1 Assessments shall be made to determine the need for additional resources based on the 

nature of and extent of the scene(s), including the approximate number of victims/decedents, and 

apparent injuries. This assessment is a continuous process until the scene is transferred to scene 

personnel.

4.5.2 The responding LEO is responsible for notifying additional units. This may include

supervisors and supporting units.

4.6 Scene Containment and Control

4.6.1 Once an assessment of the scene has been made, responding LEO(s) shall establish 

boundaries in order to control crowds and / or to restrict access into areas which may have the 

potential of containing evidence. Movement throughout the scene should be limited to essential 

personnel only. Do not permit additional LEOs to traverse the scene unless absolutely necessary. 

The initial responding LEO(s) shall make a reasonable effort to:

a) Control all individuals at the scene—prevent individuals from altering/destroying 

physical evidence by restricting movement, location, and activity, while ensuring and maintaining 

safety at the scene.

b) Identify and record all individuals at the scene, such as suspects, witnesses, bystanders, 

victims/family/friends, law enforcement, medical and other assisting personnel.

c) Exclude unauthorized and nonessential personnel from the scene (e.g., law enforcement 

officials not working the case, politicians, media).

d) Secure the scene. Set up physical barriers (e.g., ropes, cones, barrier tape, available 

vehicles, personnel, other equipment) or use existing boundaries (e.g., doors, walls, gates) 

provided that such actions are documented.

e) Document the entry/exit of all people entering and leaving the scene once boundaries 

have been established.

f) Protect the scene. Control the flow of personnel and animals entering and leaving the 

scene to maintain integrity of the scene.

g) Institute measures to preserve/protect evidence that may be lost or compromised (e.g., 

protect from the elements (rain, snow, wind) and from footsteps, tire tracks, sprinklers).

h) Consider search and seizure issues to determine the necessity of obtaining consent to 

search and/or obtaining a search warrant.

4.7 Evidence Preservation
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4.7.1 Every item located within the scene should be considered as possibly evidentiary in 

nature. 

4.7.2 Physical evidence and scene conditions shall be preserved and left undisturbed to allow a 

thorough investigation by scene investigators. Items should not be added (e.g., disposable gloves, 

food or drink, cigarette butts) or removed from the scene (e.g., weapons or drugs). Exigent 

circumstances (e.g., weather, perishable evidence) may necessitate early collection or additional 

preservation steps.

4.8 Turning Scene Over to Investigators 

4.8.1 The initial responding LEO(s) at the scene shall provide a detailed scene briefing to the 

investigator(s) in charge of the scene. Once a determination has been made to turn the scene over 

to investigators, the initial responding LEO(s) should concentrate on scene and/or personnel 

security.

4.9 Document Actions and Observations

4.9.1 All activities conducted, and observations made at the scene shall be documented as 

soon as possible after the event to preserve information. The initial responding LEO(s) at the 

scene shall produce clear, concise, documented information. The following shall be documented:

a) Observations of the scene, including the location of persons and items within the scene 

and the appearance and condition of the scene upon arrival.

b) Conditions upon arrival (e.g., lights on/off; shades up/down, open/closed; doors and 

windows open/closed; smells; ice, liquids; movable furniture; weather; temperature; and 

personal items.)

c) Personal information from witnesses, victims, suspects, and any statements or comments 

made.

d) The LEO(s) actions and actions of others that alter the scene.

e) Any known changes. If it is essential to move items, the original location and state of the 

item shall be recorded prior to movement as well as who moved the item, why, and to where.

f) Any transfer of evidence, through departmental mechanisms for chain of custody. 
Standard for Initial Response at Scenes by Law Enforcement

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Annex A

(informative)

Bibliography

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

3] ISO/FDIS 21043-2:2018(E) Forensic sciences- Part 2: Recognition, recording, recovery, transport 

and storage of material.