In 1997 the Oregon legislature passed what was then-referred to as Senate Bill 936. Senate Bill 936 made a number of changes to Oregon criminal defense statutes. No change was perhaps more significant than the addition to Oregon's evidence code of section 404(4). This section fundamentally changed the way in which Oregon courts treated an entire class of evidence commonly referred to as "prior bad acts" evidence.
In the American criminal justice system the admission into evidence at trial of other prior acts of a criminal defendant was traditionally narrowly circumscribed. The essential rule was that, subject to narrow exceptions, such prior bad acts were not admissible as improper evidence of the "bad character" of the accused. The rule was designed to insure that a jury decided guilt or lack thereof on evidence of the particular crime at hand and not on whether or not the defendant was more likely to have committed the current offense because they had done other bad things in the past. The rule of evidence concerning such prior bad acts was a "rule of exclusion:" Courts generally presumed such evidence was inadmissible unless the government demonstrated it fell within one of number of narrow exceptions.
With the enactment of Rule 404(4) the old rule of exclusion (still found in the evidence code at section 404(3)) was transformed into a rule of inclusion - that is such evidence was now to be considered admissible for any purpose, subject only to very narrow, generally constitutional rules. Almost immediately, Oregon judges and attorneys began to struggle with the application of the new rule. Questions about how the new rule related to the old rule arose. Questions as to the standards courts should employ to judge the admissibility of such evidence abounded.
Now some 18 years after its enactment the Oregon Supreme Court has finally weighed in here, holding that the new rule of inclusion does supersede the old rule of. Thus, prior bad acts evidence is now generally admissible for any purpose - including the historically prohibited purpose of proving the accused's bad character.
However, in a small nod to the potential for great abuse in the admission of such evidence, the Court held that in analyzing whether or not to admit such prior bad act evidence the Court should balance the need for such evidence against the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay or needless presentation of cumulative evidence. If such a danger or dangers "substantially outweigh" the probative value of the evidence the court may exclude it from the jury's consideration.