[1] Contaminated evidence can be brought in by witnesses, suspects, victims, emergency responders, fire fighters, police officers and investigators.
This requires crime scene investigators be especially careful to guard against contamination in the forensic samples.
If spatial relationships of the evidence are important or if something needs to have proportional measurements included in it for calculations (such as bullet trajectory angles, accident reconstructions, etc.
[4] Once the crime scene has been thoroughly documented and the locations of the evidence noted, then the collection process can begin.
from a crime scene can be collected in plastic containers at the scene and transported back to an evidence receiving area if the storage time in plastic is two hours or less, and this is done to prevent contamination of other evidence.
Once in a secure location, wet evidence, whether packaged in plastic or paper, must be removed and allowed to air dry completely.
[6] Not only is the actual crime scene as a whole important to protect in order to avoid contamination the tools used pose just as big of a threat.
Fingerprint brushes, for example, can retain the DNA they pick up and create contaminated evidence.
[1] If one fails to do so, they can be contaminated by obvious reasons like touching blood and other fluids, but also simple movements such as covering your mouth when you sneeze and scratching your face.
Many trials involve highly technical testimony about the chemistry and biology of evidence and the physics of how it was analyzed.
Unidentified evidence such as latent fingerprints, shoe tracks, hair, blood, and DNA swabbing will need to be identified.
[1] Twenty-year-old Adam Scott was charged with the rape of a woman after his saliva came upon a plastic tray that was reused.
This fault in a procedure by a worker at LGC caused Adam Scott to be jailed for five months before the mistake was later picked up on.
After investigating the process in which the DNA was collected, they discovered that a single pair of scissors was used to cut both woman's nails.
[8] Indicted for murder after his involvement in a head-on collision that killed one and injured himself and two others, Cory Carroll was released after evidence was determined not to be admissible.
After taking a urine sample at the hospital, his results came back positive for high levels of THC.