We just learned about the Fingerprints.
Another part of forensic science is Toxicology.
Long ago when someone died and it was a mystery, it was very hard to tell what happened.
If a bad person had killed someone by using poison, there was no good way to prove it so they could be sent to jail.
In 1832, a scientist named James Marsh came up with a test that could be used to show if a poison called arsenic was used to kill someone.
Arsenic did not have a smell or a strong taste, so people would sometimes sneak it into someone's food to poison them.
With the Marsh test, they would take some liquid from the body of the person that was poisioned.
Either some blood, or saliva (or spit) from their mouth, or urine from their bladder.
That liquid would be put into a bottle with some other chemicals, then burned up with some other gases, and then if it left a silvery black stain after being burned, it was proof that arsenic was used.
After Marsh proved to everyone that this test worked, it was used by police all over the world to put people in jail for trying to poison other people!
Because this worked so well, people worked on coming up with other ways to test for chemicals in a person's body.
These days scientists can test hair, blood, saliva, sweat or even food that is in the intestines that was not totally digested yet.
Toxicology helps the police prove what the truth is, using the evidence that is in the body!
(from: wikipedia - marsh test)
Kid Facts - Blast from the past: Liquid Rocket Propellants
