## Facts

- David Leon Johnson was indicted on three counts of lewd conduct with a minor, based on allegations that he sexually abused his daughter, A.J., when she was approximately six to seven years old.
- Two counts concerned alleged incidents during spring break weekend in 2004 while A.J.’s mother was out of town; a third count concerned an alleged incident during Memorial Day weekend in 2005.
- A.J. testified to molestation corresponding to the first two counts.
- The State sought to introduce testimony from Johnson’s younger sister that Johnson sexually abused her when he was about fifteen and she was about seven or eight.
- The district court admitted the sister’s testimony under Idaho Rule of Evidence 404(b) as evidence of a “common plan,” relying on similarities in the victims’ ages, family/authority relationship, and the nature of the alleged conduct.
- The jury convicted Johnson on two counts and acquitted him on the third; the court imposed unified 15-year sentences with 5 years fixed on each count.

## Issues

1. Whether the district court erred under Idaho Rule of Evidence 404(b) by admitting testimony that Johnson had abused his sister as a teenager on a “common plan” theory rather than for a proper non-propensity purpose.
2. Whether, even if relevant for a non-character purpose, the testimony should have been excluded under Idaho Rule of Evidence 403 as unfairly prejudicial.
3. If the admission was error, whether the error was harmless.

## Decision

- The Idaho Supreme Court held the district court erred by admitting the sister’s testimony as “common plan” evidence under Rule 404(b).
- The Court concluded the testimony operated as impermissible propensity evidence rather than proof of a genuine plan or other allowable purpose.
- The Court further determined the evidence’s unfair prejudicial effect substantially outweighed any legitimate probative value under Rule 403.
- The Court held the error was not harmless given the credibility-centered nature of the case and the powerful impact of the prior-acts testimony.
- The convictions were vacated and the case was remanded for a new trial.

## Legal Principles

- Rule 404(b) bars other-acts evidence offered to prove character and action in conformity; it is admissible only for a specific, non-character purpose (e.g., motive, intent, plan, identity) supported by a logical relevance other than propensity.
- In child-sex-abuse prosecutions, Rule 404(b) applies with the same limits as in other criminal cases; similarity to prior sexual misconduct does not alone establish admissibility.
- A “common plan” requires more than resemblance between prior and charged acts; the evidence must show an actual plan or scheme linking acts in a way that does not depend on inferring disposition.
- Even when other-acts evidence has some non-propensity relevance, it must be excluded under Rule 403 if unfair prejudice substantially outweighs probative value, particularly where the case turns on credibility.
- Erroneous admission of highly prejudicial propensity evidence is not harmless where there is a reasonable probability it affected the verdict.

## Conclusion

The Idaho Supreme Court reversed Johnson’s convictions because testimony about alleged sexual abuse of his sister when he was a teenager was inadmissible propensity evidence mislabeled as a “common plan,” was unfairly prejudicial under Rule 403, and likely influenced the verdict in a credibility-driven trial.


State v. Johnson, 148 Idaho 664, 227 P.3d 918 (Idaho 2010)