§ 9.02. Forensic-Evidence Collection

Agencies should collect forensic evidence in an impartial, consistent, and thorough manner, designed to maximize accuracy. In doing so, agencies should rely on:

  • (a) the participation of, and guidance from, scientists and crime laboratories;
  • (b) specialists in conducting crime-scene-evidence collection; and
  • (c) written evidence-collection policies.


a. Sound collection of forensic evidence. Failure to collect, or properly collect, forensic evidence can result in loss or contamination of that evidence. At the crime scene, the assumptions of investigators can affect decisionmaking about what to collect and how to collect it. It is crucial that evidence collection be conducted in a manner informed by scientific methods so that evidence is not lost or altered. Scientists and crime laboratories should be involved in guiding, if not also conducting, evidence collection and preservation.

b. Crime-scene specialists. Currently,crime-scene-evidence collectors can include uniformed officers, detectives, crime-scene investigators, criminalists, forensic scientists, coroners, medical examiners, hospital personnel, photographers, and arson investigators. Crime-scene units and investigators with specialized training in crime-scene investigations, who possess a grounding in scientific principles and research will perform work that is more consistent and accurate. Accordingly, they should be used whenever possible.

c. Scientific oversight boards. Agencies (or even better yet, jurisdictions) should create scientific-advisory and oversight boards to formalize the participation of and guidance from scientists. Doing so can ensure that scientific standards are adopted and followed within policing agencies and crime laboratories. Such bodies should routinely audit and assess the quality of the actual work performed by agencies, and not just review written policies and procedures.

d. Written policies. Agencies and crime laboratories should adopt written policies regarding evidence collection that are based on input from scientists and scientific organizations. Such policies should set out procedures for evidence collection. They also should be updated periodically to reflect new research and technology.

Reporters’ Notes

The “most fundamental” issue affecting the use of forensic science is that “[t]race evidence cannot be used unless the police are aware of its existence and usefulness and know how to collect and preserve it.” Mike Redmayne, Expert Evidence and Criminal Justice 23 (2001). The manner in which forensic evidence is collected should be consistent with scientific standards. It is crucial that scientists and crime-lab professionals participate in the development of policies and guidelines governing evidence gathering and management, and in the process of evidence gathering and management itself. Scientific and forensic organizations have rules of conduct concerning evidence gathering and management. See, e.g., National Forensic Science Technology Center (NFSTC), Crime Scene Investigation: A Guide for Law Enforcement (2014); Sue Ballou et al., The Biological Evidence Preservation Handbook: Best Practices for Evidence Handlers (NIST, 2013).

Due to resource constraints,evidence collection is not always performed by trained professionals.Frank Horvath & Robert T. Meesig, A National Survey of Police Policies and Practices Regarding the Criminal Investigation Process: Twenty-Five Years After Rand 76 (2001), https://www.ncjrs.gov/pdffiles1/nij/grants/202902.pdf. (“[I]n most agencies evidence-related duties are not assigned predominantly to any one type of individual or position. Rather, they are more likely to be shared among patrol officers . . . investigators . . . and evidence technicians[.]”). The primary engines of evidence collection typically are patrol officers, who may be the most junior, least trained, and most overtasked personnel in the hierarchy. Jennifer E. Laurin, Remapping the Path Forward: Toward A Systemic View of Forensic Science Reform and Oversight, 91 Tex. L. Rev. 1051, 1081 (2013). According to one survey, 52 percent of U.S. crime labs engaged in crime-scene response activities, and both county labs (62 percent) and municipal labs (71 percent) were more likely than state labs (44 percent) to be directly involved in crime-scene investigations in 2009. Matthew R. Durose et al., Bureau of Justice Statistics, U.S. Dep’t of Justice, Census of Publicly Funded Forensic Crime Laboratories, 2014 7 (2016). Often police agencies gather evidence at crime scenes.

The lack of standards, training, and oversight in crime-scene work can result in mistakes made because of haste, inexperience, or lack of a scientific background, as well as more serious quality-control failures and misconduct. Nat’l Research Council, Comm’n on Identifying the Needs of the Forensic Scis. Cmty., Strengthening Forensic Science in the United States: A Path Forward 56-57 (2009). Guidance from scientists and crime laboratories can help agencies prioritize when and whether to collect evidence for forensic analysis. A recent study sponsored by the National Institute of Justice revealed that across four urban jurisdictions, some physical evidence was collected in nearly all homicide investigations initiated during the study period, but in only 30 percent of assault investigations, and only 20 percent of burglary investigations. Peterson and Sommers found that biological evidence—quintessentially associated with sexual-assault investigations—was collected in only 54 percent of investigations. Joseph Peterson & Ira Sommers, The Role and Impact of Forensic Evidence in the Criminal Justice Process 22 (2010).

In the past, much of the work in promulgating and encouraging best practices for evidence collection has fallen to individual policing agencies or to crime laboratories, but often those practices and policies have not been well coordinated. Thanks to Combined DNA Index System (CODIS) regulations, crime laboratories face their own legal requirements for documenting and certifying the integrity of evidence they receive. Laurin, supra, at 1086; Julie Samuels et al., Collecting DNA from Arrestees: Implementation Lessons, 270 Nat’l Inst. Just. J. 18, 22 (2012). Policing agencies may have different procedures for those tasks. There should be more coordination between policing agencies and crime labs to ensure integrity in evidence collection. See, e.g., Jan S. Bashinski & Joseph L. Peterson, Forensic Sciences, in Local Government Police Management 488, 503-504 (2003) (advocating for coordination); John K. Roman et al., The DNA Field Experiment: Cost-Effectiveness Analysis of the Use of DNA in the Investigation of High-Volume Crimes 11 (2008) (describing how collaboration is critical and describing the breakdown in evidence collection in some jurisdictions because of poor coordination); Richard Saferstein, Criminalistics: An Introduction to Forensic Science 6-8 (7th ed. 2001) (advising coordination but noting the lack thereof in many agencies). Uniform standards for evidence collection, retention, and preservation could bolster investigation practices and significantly reduce the chances of wrongful arrest, prosecution, and conviction. Working collectively with other law-enforcement agencies in a jurisdiction would further enhance this recommendation and perhaps reduce the resource burden. International Association of Chiefs of Police & U.S. Dep’t of Justice, National Summit on Wrongful Convictions: Building a Systemic Approach to Prevent Wrongful Convictions 15 (2013). As described in the Reporters’ Notes to § 9.01, agencies and, preferably, jurisdictions also can establish scientific oversight bodies to produce such uniform standards, as well as provide oversight regarding written policies but also the quality of the work performed, in order to accomplish the quality-control goals of these Principles.

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