Investigations | Section 1.5

Fundamentals of Criminal Investigation by Adam J. McKee

Section 1.5: Crime Scene Procedures

If you ask any experienced detective or crime scene technician to identify the top five most serious and common problems they find at crime scenes, you will inevitably hear the same response within those five: Curious officers, supervisors, and detectives contaminate crime scenes with disturbing regularity.  The inadvertent contamination of crime scenes is a serious problem that will not go away without effective departmental policies that are explained and reinforced through rigorous training. This training needs to include all police officers and support staff, not just crime scene technicians and detectives. First responders are obviously the first on the scene, and they will frequently contaminate scenes if they are not trained in proper protocols.  

Hollywood has generated a multitude of myths about criminal justice, and crime scene investigation has not escaped the trend of misinformation.  Television murder scenes are always staffed by a dozen or so uniformed officers, several detectives, an (often angry) lieutenant, and a few crime scene technicians wandering around snapping random pictures and dusting (haphazardly) for fingerprints.  This is precisely the opposite of what should occur. Absolutely no one who is not absolutely necessary to carry out the investigation should be allowed into an active crime scene.

Hordes of curious officers stampeding a crime scene is a recipe for disaster.  Few things can damage an investigation more seriously and irrevocably. The more sensitive the type of evidence, the more serious the problem of contamination becomes.  DNA analysis, blood splatter interpretation, and the analysis of trace evidence becomes much more difficult if not impossible. Collecting hair samples, for example, becomes an exercise in futility when twenty officers have passed through the search space. Footwear, tire tracks, and other impression evidence can become worthless, even on the fringes of the crime scene when many unnecessary personnel are mulling about.

Supervisory Role

The first line of defense for crime scene integrity comes from supervisory personnel setting good policy and good examples for line officers.  Ultimately, supervisory personnel, including detectives, are responsible for investigations. Investigators who severely curtail access to active crime scenes do so to preserve the scientific integrity of forensic evidence, as well as preserving the legal integrity of the evidence so that it will later be admissible in court.  The behavior of supervisory personnel can go a long way in teaching curious officers to stay away from crime scenes to avoid contamination. Leaders must be self-disciplined enough to follow departmental policies (which need to be based on best practices) such as rigorously maintaining entry and exit logs, not entering a crime scene without a legitimate investigative purpose, and so forth.   Peeking in cabinets and digging around in drawers sets the opposite example, and ultimately degrades the overall professionalism of the department.

Written Policies

Another major responsibility of departmental leadership is to develop clear policies concerning crime scene protection and preservation.  The policy cannot be taken lightly; it needs to have the same force as other departmental policies, and supervisory personnel needs to make sure that the policy is carefully followed by all officers.  It is easy to forget that patrol officers are the first on most scenes and that they need to be trained and guided into correctly securing, protecting, and preserving crime scenes. It must be made known to all officers, regardless of rank, that inquisitiveness is no excuse for entering a crime scene without an investigative role to play.  When formulating policy, administrators would be wise to consult district attorneys that have lost cases due to crime scene contamination. In addition, crime laboratory staff should be considered as well.

A key goal of a crime scene policy should be to provide a set of uniform procedures to restrict unnecessary access to active crime scenes.   A necessary element of such a policy is that a single point of entry should be established and that the officer assigned to that main entrance must log every person entering and exiting the scene, along with the time of the entry or exist.  Along with the person’s name and rank, the reason for the visit should be recorded. A policy (and the related standardized form) that asks the purpose of entering the scene serves as a reminder that only persons with legitimate investigative roles should enter.  The policy must absolutely prohibit entry by all undocumented persons.

The policy should direct all officers (and civilian support staff if applicable) entering the scene to write a standardized report detailing what they did at the scene.  Anyone entering the scene must make themselves available to produce elimination samples (e.g., hairs, fingerprints, and saliva). In an effort to eliminate “tourism” at crime scenes, many departments have adopted a policy that requires the highest ranking officer to enter the scene to take responsibility for all personnel at the scene.  This means that high ranking officers wanting to “have a look around” cannot leave the scene until all other officers and technicians have finished their work or an officer of higher rank arrives.

Often, the officer tasked with security of the scene will be a patrol officer who is placed in the untenable position of telling higher ranking officers not to enter the scene.  Clear, written policies can go a long way in protecting the integrity of the scene. Senior staff should keep those power dynamics in mind when drafting policies that not only look good on paper but which can be implemented by officers in the field.  

Ultimately, even the best-designed policies are useless if they are not properly implemented in the field.  The high cost of crime scene contamination must be understood by every officer within a department, not just detectives.  Best practices dictate that rookie officers be trained on crime scene protection and the preservation of evidence at the academy and that these important lessons be reinforced through in-service training at periodic intervals.

Key Terms

References and Further Reading

Technical Working Group on Crime Scene Investigation. (2000).  Crime Scene Investigation: A Guide for Law Enforcement.  Available:


Modification History

File Created:  05/02/2019

Last Modified:  04/30/2021

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This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

Open Education Resource--Quality Master Source License


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