Criminal Investigation: Understanding Properly Handling Blood Evidence

Blood evidence is a valuable resource in a criminal investigation, but it is extremely fragile. Mishandling can easily damage or even destroy this type of evidence, potentially endangering the successful investigation and/or prosecution of the pertaining case. Ultimately, many precautions need to be taken while handling blood evidence so it is not contaminated or ruined before it can be helpful to the case. In the end, blood evidence can make or break a criminal investigation or case because it often can (1) identify and/or eliminate possible suspects, (2) verify and/or contradict witness or suspect testimony, and (3) serve as a guide for many parties, including investigators, judges, and juries (Schiro, n.d.).

Communication is Key

I would like to outline some guidelines for properly handling blood evidence. First, communication is critical for properly collecting this kind of evidence. Individuals at the crime lab, first responders, and investigators should all communicate with one another so they can approach blood evidence in a unified fashion and know when procedures change (Schiro, n.d.). Furthermore, the office's evidence policy and procedures should be clearly written down and made available to all personnel so everyone can know the proper way to handle blood evidence.

Proper Collection & Preservation of Blood Evidence

Here are some guidelines specifically dealing with how to properly collect blood evidence.

(1) Assess and document the scene before beginning to process any evidence. This allows you to make a record of where evidence is, while giving you an idea of what evidence needs to be removed first (Schiro, n.d.).

(2) Develop an evidence collection plan. Since blood evidence is usually the most fragile, it should be gathered first, along with any other type of evidence that is at risk of being destroyed or damaged.

(3) Use new and clean paper containers to package all evidence (e.g., packets, envelopes, etc.) and use separate containers if different types of evidence might contaminate one another.

(4) If you can, allow all wet evidence to dry before packaging.

(5) But if the scene does not allow for this, plastic containers can be used until the evidence can be taken back to evidence storage and dried (can't be left in plastic more than 2 hours).

(6) Just as important, make sure all blood evidence is clearly labeled with the collector's name/initials, case or police number, when and where it was found, what the evidence consists of, and what department it belongs to (Evidence collection guidelines, n.d.; Schiro, n.d.).

(7) Always avoid exposing blood evidence to humidity and heat, since this can degrade or even destroy useable DNA.

(8) Because of its delicate nature, blood evidence should be either refrigerated or sent to the lab as soon as possible.

(9) All precautions (e.g. gloves, masks, etc.) should be taken to avoid contact with this evidence. Not only can investigators contaminate blood evidence, such evidence is very hazardous to their health.

(10) Preferably, the entire object that the blood evidence is found on should be packaged since removing it can sometimes compromise it (Evidence collection guidelines, n.d.; Schiro, n.d.).

(11) However, if it is too large to package, there are four acceptable methods to remove the evidence. First, for dried stains, you may choose to cut out the blood from the object, taking care to include samples with and without the blood. You may also use fingerprint tape to remove the blood from the object like you would a fingerprint, taking great care not to touch the sticky side of the tape. Moreover, you can use a clean sharp instrument to scrap the evidence off the object into a paper packet. And finally, it is also acceptable to use moistened 1/2" long threads (swabs) or moistened 1/2" x 1/2" cotton squares to absorb the blood evidence. Wet blood evidence, on the other hand, can be removed from a large object by using 1" x 1" cotton muslin squares to absorb the blood (Evidence collection guidelines, n.d.; Kramer, n.d.; Rhode Island State Health Laboratories, 2007; Schiro, n.d.).

References:

Evidence collection guidelines. (n.d.). Retrieved November 3, 2007, from http://www.crime-scene-investigator.net/collect.html

Fisher, B. A. J. (2004). Techniques of crime scene investigation (7^th ed.). Boca Raton: CRC Press.

Kramer, R. E. (n.d.). DNA and evidence collection principles. Retrieved November 3, 2007, from http://www.geocities.com/cfpdlab/DNA.htm

Rhode Island State Health Laboratories. (2007). Forensics: Evidence collection in forensic biology. Retrieved November 3, 2007, from Rhode Island Department of Health Web site: http://www.health.ri.gov/labs/forensic_evidence.php

Schiro, G. (n.d.). Collection and preservation of blood evidence from crime scenes. Retrieved November 4, 2007, from http://www.crime-scene-investigator.net/blood.html