Locating files and evidence

Locating the case file and original evidence for the investigation may be a challenging endeavor. Changes in personnel, procedure, and facilities and the passage of time may complicate the process. When searching for a case file or evidence, an investigator may need to look in numerous places. Potential locations include, but are not limited to, the following:

• Police department property rooms (case files, evidence logs, whole evidence).
• Property warehouses (case files, evidence logs, whole evidence).
• Public crime laboratories (previously tested/submitted evidence, lab reports).
• Private laboratories (previously tested evidence, lab reports).
• Hospital/medical facilities (rape kits, medical reports, slides).
• Coroner/medical examiners' offices (autopsy reports).
• Courthouse property rooms.
• Prosecutors' offices (previous trial or suspect investigation).
• Retired investigators' files (case notes and details not contained in file).
• Other investigating agency offices (investigative leads--serial offender).

Forensic testing reports and previously tested evidence

Because advancements in DNA technology enable laboratories to successfully analyze old evidence that might have been improperly stored or subjected to previous forensic analysis, it will be very valuable to locate any and all forensic reports that were produced as a result of previous analysis and/or testing. ABO blood typing, microscopic hair analysis, RFLP DNA analysis, or fingerprint analysis (among others) might have been performed in the course of the original investigation. The original case file should indicate whether and which types of forensic analysis were attempted. These reports also serve to memorialize proper chain of custody. Cooperation with the crime laboratory is crucial to locate and interpret existing forensic reports and to determine whether evidence would be amenable to reanalysis with new DNA techniques.

Many combinations of options are available to investigators and laboratory personnel if biological evidence was available and previously tested.  See "Investigative Options ," which may serve to help investigators as they work with the laboratory to discuss options throughout the course of the investigation.

Locate biological evidence

When reviewing the case file for potential DNA evidence, it is important to know what kinds of evidence may yield a DNA profile. Given the power and sensitivity of newer DNA testing techniques, DNA can be collected from virtually anywhere. Only a few cells can be sufficient to obtain useful DNA information to help solve a case. See "Common Evidence ," which identifies some common items of evidence that may have been collected previously but not analyzed for the presence of DNA evidence. Remember, if a stain is not visible it does not mean that there are not enough cells for DNA typing. Further, DNA does more than just identify the source of the sample; it can place a known individual at a crime scene, in a home, or in a room where the suspect claimed not to have been. It can refute a claim of self-defense and put a weapon in the suspect's hand. It can also provide irrefutable evidence that can change a suspect's story from an alibi to one of consent.

Some or all of the content on this page was excerpted from the Special Report Using DNA to Solve Cold Cases, developed under an award from the Office of Justice Program's National Institute of Justice. See award product disclaimer.