Wrongful conviction
Pieces of evidence may be contaninated, while they are packaged or transported. Contamination can be introduced unintentionally by material that was not present when the crime was committed by anyone entering the crime scene after the event - by uninvolved witnesses who may become suspects, and by emergency responders, fire fighters, police officers and crime scene investigators themselves. If proper protocols are not followed, evidence can also be contaminated when it is being analyzed or stored. A miscarriage of justice can occur when procedures to prevent contamination are not carried out carefully and accurately.