Forensics helps figure out who committed a crime and there are plenty of types of forensics like people who study fingerprints because everyone has different one no one has the same
Ballistics Expert they study guns and bullets that helps a lot like how far they where or where they are standing to find out what gun was use. 
Deoxyribonucleic Acid they study DNA from things like hair small pieces of skin blood and ECT. then they match it to things from the crime. 
Pathologists study how people die. That helps by telling them how that crime was committed fun fact they get paid the most out of all of the types of forensics sciences they get around 200,000 to 300,000.
