Pennsylvania Rule of Evidence generally prohibits the admission of what is know as "other bad act" evidence. Other bad act evidence is any evidence that references a bad act in the defendant's past. This evidence does not only apply to convictions or cases where criminal charges were filed, but includes uncharged bad acts as well. The purpose behind this exclusionary rule is to prevent the Commonwealth from admitting evidence to make the accused look like a bad person. In order for the Commonwealth to admit this type of evidence, it has the burden of proving this evidence does not go to show that a person is of bad character, but rather that the evidence can show the defendant's motive, intent, modus operand, knowledge, or plan. This evidence must be presented to the trial judge during a pre-trial motion. Lastly, admission of this type of evidence leads to the most reversible errors at the Superior Court.