Student question: What is biological evidence and how does it help in an investigation?
In a nutshell, biological evidence can be any substance from a human source providing personal identification of that source. The power behind biological evidence is its use in identifying victims or suspects, leading to establishing the presence of victim or suspect being at a scene.
Types of biological evidence include body fluids, such as blood, semen, saliva, and urine, as well as skin and other types of tissues and organs.
Biological evidence helps in proving or disproving an alibi, eliminating a suspect, identifying a suspect, and identifying a victim. DNA evidence taken from a crime scene can be compared to DNA taken from a suspect or victim.
New technologies and methods, including the collection of trace amounts of DNA (touch DNA) and forensic genealogy, has revolutionized the use of biological evidence taken decades ago in the hopes of solving cold cases and proving innocence (or guilt).
When collecting biological evidence, collection methods and conditions must be taken into consideration. It is best practice to use sterile and disposable when collecting samples, and the prevention of personal exposure to biohazards such as HIV, hepatitis, herpes, and other transmittable diseases and/or bloodborne pathogens, must be avoided at all costs. This is not only for the prevention of cross contamination of the evidence but for the forensic personnel collecting the evidence.
Evidence should be packaged separately, and depending upon the type of evidence, proper collection containers, such as paper bags, are used. For example, small pieces of evidence, such as hairs or fibers, should be collected in small coin-type envelopes. Hairs collected form other items of evidence should be packaged with original piece of evidence.