Why are there rules of evidence?

Question

For example, if there was a murderer whom everyone knew was guilty, but a key piece of evidence was thrown out, and therefore the jury would not be able to convict. Why does the government allow this even when it is obvious that the defendant is guilty?

Answer 1

The evidence must have been obtained illegally, such as no warrant, or going outside what the warrant specified for a search.

Answer 2

If there were no rules at all, then confessions obtained under torture would be allowed, and your opinion that the defendant is guilty would have equal weight to testimony of someone who places the defendant five thousand miles away at the time of the crime.

There have to be rules, the question is where the lines are drawn.

First thing the rules exclude is anything that doesn't have anything to do with the case, or isn't "factually based". This is to shorten the trial, and to not confuse the jury by them hearing evidence of how evil someone is generally, when the question is whether or not they did this one specific act.

The things you're more concerned about are pieces of evidence that would pretty much be "slam-dunk" if allowed, but are excluded because they are improperly obtained. The exclusion is because that's pretty much all the courts can do to be sure they don't come knocking on YOUR door at 2am and toss your house looking for anything that might be evidence of something.

There is no perfect system.

Answer 3

Rules of evidence are in place to make sure the information a jury (or in some cases a judge) uses to make a decision is as reliable as possible. Since defendants are presumed innocent, the law basically gives them the benefit of every doubt.

Answer 4

Evidence may be unreliable.

Evidence may be irrelevant.

Evidence may not give a defendant an opportunity for cross-examination or rebutal (e.g. hearsay evidence)

Some evidence may violate principles that we, as a society, wish to maintain, even at the expense of letting a guilty party go free (e.g. evidence of conversations with clergymen, doctors and psychiatrists, attorneys, and spouses)

Some evidence would question the integrity of the judicial process (e.g. evidence obtained in violation of Constitutional provisions).

There are lots of reasons.

Answer 5

Both of the posters ahead of me are right...
There have to be rules...or else tainted evidence, false statements and the like, would also be allowed.
When laws and rules are written, they are written to try to cover the broadest base of situations. However, since no two situations are EXACTLY the same, there are going to be some situations where the rules can work for...or against you...and have to be applied no matter what....
Like double jeopardy...a law I have a hard time with sometimes..
Flawed though our US system may be...it's all we have...it works MOST of the time...and it's the best "out there"...

Answer 6

In order to protect the due process rights of EVERY defendant, no tainted evidence is allowed.

Answer 7

becasue with out the key peice of evidence it cannot be proved beyond a reasonable doubt.