Maximizing Forensic Science Capabilities in Criminal Investigations
Written by Mark Vecellio   

THE USE OF FORENSIC SCIENCE to support criminal investigations is widely recognized. Probably due to mass media and entertainment exposure, it seems that just about everyone understands that scientific analysis of physical evidence is used to bolster criminal investigations. Research and practitioner observations clearly illustrate that investigations with physical evidence and supporting forensic examinations are more often solved and fare better once in the judicial system. With this in mind, it would seem reasonable to believe that most investigations result in the recovery and forensic testing of physical evidence. The reality, however, paints a different picture.

Though vastly under-studied, the few studies that do exist reveal that investigators collect physical evidence at an alarmingly low rate in certain types of criminal investigations. Studies in the states of Indiana and Connecticut revealed that police collected physical evidence in less than 30% of assault cases, 20% of burglary cases, and 25% of robbery cases. Moreover, in the Indiana sampled cases, much of the evidence that was collected never made it to the crime laboratory for scientific analysis. The data reported in the studies is consistent with my personal observations gathered throughout my 23-year career. In light of the advances in technology, education, and training in forensic sciences, one is forced to question why the rates of evidence collection appear to be so low across a broad spectrum of criminal investigations.

I believe that formulation of a clear and explicit strategy in casework can improve an agency’s ability to both recover physical evidence and ensure relevant forensic testing is completed. I refer to this strategy within the scheme of case management as “forensic strategy.” As with any complex task, having a strategy can help maximize effectiveness and efficiency. Yet, based on my observations from working with various city, county, state, and federal agencies, I submit that many investigators employ no such strategy in regard to forensics or physical evidence. Investigators commonly employ investigative plans to help organize their efforts, but when it comes to forensics, planning and strategy is often absent, fragmented, and undocumented.

Employment of a specific strategy at or near the inception of a criminal investigation can yield tremendous success, in terms of identifying and recovering physical evidence, as well as in yielding useful information derived from forensic examinations of the recovered evidence. This strategy should be formulated as soon as practically possible; most certainly before the crime scene is fully processed. The investigator should consider what types of physical evidence could contribute to a more thorough understanding of the crime or particular relevant events related to the crime. Since criminal investigations usually involve proving multiple legal elements of the crime along with probing various other issues, the initial forensic strategy should be relatively broad in focus. Later, as new information and evidence is collected and analyzed, this strategy should be modified, and potentially narrowed, to suit the current case facts and circumstances.

Investigators should formulate a clear, concise strategy during the initial stages of an investigation. Doing so will improve the likelihood that relevant physical evidence is identified at the crime scene. Photo: Erick Bryant, Crime Scene Analyst, Colorado Bureau of Investigation

The Process

Phase I: Formulate the Initial Strategy

This initial strategy, as described above, will guide investigators to search for specific forms of evidence, in addition to any obvious items, observed at the crime scene or other locations. Formulation of this strategy at the onset prompts the investigator to start thinking about physical evidence right out of the gate. Though this may seem to be “common sense,” my experience (and the aforementioned research data) dictate otherwise. Often, initial responses to scenes are hectic, and though preservation and collection of evidence is clearly emphasized, key items may be overlooked.

Development of an explicit initial forensic strategy, even if abridged, will help investigators maintain proper awareness of what physical evidence should be sought. This initial strategy will, of course, be dependent on the facts and circumstances of the case. In some cases, it may be necessary to prove the suspect was at the crime scene or had physical contact with the victim, but in other cases, these issues may not be relevant. An example would be a domestic assault. In this kind of case, more subtle evidence—such as damaged items, correspondence, or injury documentation—may be critical.

Again, the premise of the initial formation of the forensic strategy is to prompt investigators to critically think about physical evidence and how such evidence may be useful.

Phase II: Written Strategy

As soon as practical, the forensic strategy should be re-assessed based upon the collected information and evidence. This updated assessment should be documented in the investigative case file. Documentation serves a few purposes:

1) creates a clear record in the event the case is transferred to another detective;

2) documentation often helps investigators more concisely and thoroughly analyze how physical evidence can aid the investigation;

3) creates a historical record of the investigator’s thoughts.

This written process is similar to the formulation of a written investigative plan.

Phase III: Evolution of the Plan

The forensic strategy should evolve as additional case facts are obtained and analyzed. Case circumstances often spark new questions or issues that could help be addressed by physical evidence. Any time new, relevant case information arises, investigators should determine whether collection of additional physical evidence or re-analysis of existing physical evidence should occur. With this process in mind, the strategy should be viewed as adaptable and flexible. This adaptable process will help investigators stay focused on physical evidence throughout the entire investigative process, thus resulting in a better end product. I personally found it advisable to review the strategy every week during major, complex cases, and every two to four weeks for routine cases.

Strategy Example and Execution Tips

Within the written forensic strategy, investigators may find it helpful to first note the objectives of the strategy. For example, objectives may include showing physical contact between the suspect and the victim, linking the victim with the crime scene, determining if sexual activity may have occurred, and so on. Then, for each objective, investigators can annotate what physical evidence should be sought. Finally, for each item of evidence obtained, the investigator can describe what general scientific exams could be of assistance. To enhance this portion of the process, the detective, if not well educated in forensic science capabilities, should consult with an expert—maybe a crime scene investigator with a forensic science background or forensic scientists from supporting laboratories. Regardless of the manner in which the knowledge is obtained, the outcome should be the investigator attaining a deep comprehension of how forensic science examinations can exploit physical evidence obtained, or able to be obtained, in order to provide relevant information.

For this reason, my experience has shown that investigators with strong forensic science backgrounds and knowledge do a much better job of identifying relevant physical evidence. Some agencies employ forensic specialists to assist in this process. These specialists, when optimally utilized, are available for consultation or assistance on a 24-hour basis. Problems in identifying and collecting evidence often arise during non-business hours, so having a specialist available to answer questions or provide advice is valuable. Though coordination with forensic scientists employed in forensic laboratories is a great option, it is often simply not practical. Agencies without formal CSI personnel should consider less-costly training options available through state or federal agencies. The National Institute for Justice, for instance, offers several low-cost forensic science training courses that can vastly improve detectives’ forensic science knowledge. Most forensic laboratories publish evidence submission guides, which also can be a great source of knowledge. One such guide is the FBIs Handbook of Forensic Services.

Forming a forensic strategy is also helpful in maximizing information derived from forensic examinations of the recovered evidence. Photo: Patrick Wright, Methodist University

Case Example

Following is a simplified example of a forensic strategy that may be used in a rape investigation. (Note: Since this serves only as a sample to help readers understand the process, the strategy is abridged and only includes a few items of evidence.) In this hypothetical case, the rape victim reported she was raped by a male acquaintance after they consumed a few alcoholic drinks at her residence. According to the victim, this was the first time the suspect had been in her residence. The victim said she lost consciousness at some point, but was not sure if that was caused by her own ingestion of alcohol or something the suspect may have slipped into her drink. For this sample case, there are no eye-witnesses and the suspect did not make a statement to police.

Objective 1: Establish presence of suspect at the scene.

Evidence sought: Fingerprints, footwear impressions/prints, trace evidence, biological evidence, items left behind by suspect. Use alternate light sources to assist in search. Consider search of suspect residence to collect evidence that may have been transferred from the victim to the suspect. Collect elimination samples of prints, biological evidence if relevant (for instance, if another person lives at residence). Collect victim and suspect fingerprints and footwear if appropriate.

Objective 2: Show physical contact between victim and suspect.

Evidence sought: SAFE kits from both victim and suspect, clothing from suspect and victim. Consider search of suspect residence to collect evidence that may have transferred from the victim to suspect. Collect elimination samples if relevant.

Objective 3: Determine drug ingestion of victim/suspect and whether suspect may have administered drugs to the victim.

Evidence sought: Urine and blood samples from victim and suspect. Consider hair samples depending on time of offense. Search scene for empty containers or containers with beverages. Search of suspect home for drugs if warranted. Consider search of victim and suspect prescription histories or purchases of over-the-counter drugs.

For the purposes of this example, let’s use a few basic items of evidence to illustrate how forensic examinations can assist in the investigation (see Table 1).

Table 1. Items of evidence and potential forensic examinations


As you can see, this is a relatively straightforward process, but one that can pay immense dividends. This explicit focus on physical evidence and supportive forensic examinations will serve to generate and maintain proper focus and effort throughout the investigation. The results will be more solved cases and cases with better judicial outcomes.

About the Author

Mark Vecellio is a Professor of Applied Forensic Science at Methodist University in Fayetteville, North Carolina. He is a retired U.S. Army Criminal Investigations Command Supervisory Special Agent and Forensic Sciences Officer, including six years of service as Special Agent in Charge. Vecellio spent 23 years performing and supervising felony level criminal investigations across the world and specializes in crime scene processing/reconstruction, forensic photography, sexual assault investigations, and death investigations. He has delivered research presentations and technical workshops at the American Academy of Forensic Sciences and North Carolina Homicide Investigator's Association, published three research articles, and co-authored a book in the field of forensic photography. He currently supports local and regional law enforcement efforts through active membership in the Carolina’s Cold Case Coalition.

This article appeared in the Fall 2019 issue of Evidence Technology Magazine.
Click here to read the full issue.

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