What are the federal rules of evidence and why are they needed

The four main traditional rules are real, demonstrative, documentary, and testimonial. These laws determine what evidence must or must not be considered by the trier of fact in reaching its decision.

Explanation:

The federal rules of general provisions, judicial notice, presumptions, relevancy and its limits, privileges, witnesses, opinions and expert testimony, hearsay, authentication and identification, contents of writing, photographs and recordings. They are needed because they govern the evidence at civil and criminal trails in US federal trial courts. The current rules were initially passed by congress in 1975, after years of drafting by the Supreme courts.

the cat said meow. the police should not have shot it.

answer:

i think that is because of today's society mainly the gangbanging and ect.