DNA used as evidence has become more popular than ever. That is why understanding how DNA collected at the crime scene plays a critical role in proving a crime, and also the times that DNA proof can be denied.

How Is DNA Collected and Preserved? 

Police and investigators collect DNA samples from a source such as blood, bodily fluids (i.e., semen or saliva), hair, and skin. DNA sample collection must be done with extreme caution to prevent contamination.  

For instance, an investigator touching blood samples with their bare hands may lead to contamination of that sample. Similarly, DNA samples may become unusable if police or investigators step on them, spill something, or fail to isolate samples. 

Biological evidence, such as hair, does not require complex preservation. DNA evidence kept in air-tight containers can last for a year without significant degradation. However, special care must be taken to ensure there is no contamination.