Concerning the criminal court of the United States of America, people are innocent until proven guilty. The burden of proof lies with the prosecutor – meaning they must prove beyond a reasonable doubt that the defendant is guilty. Using evidence, they must answer three criteria to convict a person of a crime.

Motivation – a reason to commit the crime
Means – a way to commit the crime
Opportunity – a time to commit the crime

Evidence is the lifeblood of a case – evidence cannot be biased nor can it lie. The problem throughout all of history is finding the evidence.

In 1910, Edmond Locard came up with the 'exchange theory'. It states that a criminal will always leave a trace of his presence behind at the scene of a crime, and will always carry away some trace of the crime with him. These are called ‘objective traces’ or evidence, as opposed to ‘subjective traces’ which are eyewitness testimonies and suspect statements. While testimonies and statements are useful in many cases, they are usually unreliable. Evidence is undisputable, and if used right can solve a crime. The exchange theory is considered the foundation of forensic science – which changed criminal law forever. Mr. Locard called his theory

Trace Evidence

Can you solve the crime first? It’s written so you can. Remember: motivation, means, and opportunity. Pay attention to every detail!

For Brenna-bunny

Thanks to the works Handwriting Analysis, Encyclopedia of Forensic Science, Eight Minute Mysteries, Collecting Evidence, Famous Murders, Adventures of Sherlock Holmes, and the various television shows and CSI games Brenna and I exhaustively play.