In deciding what the facts are, you may have to decide what testimony you believe and what testimony you do not believe. You may believe everything a witness says or only part of it or none of it.
In deciding what to believe, you may consider a number of factors, including the following: (1) the witness's ability to see or hear or know the things the witness testifies to; (2) the quality of the witness's memory; (3) the witness's manner while testifying; (4) whether the witness has an interest in the outcome of the case or any motive, bias or prejudice; (5) whether the witness is contradicted by anything the witness said or wrote before trial or by other evidence; and (6) how reasonable the witness's testimony is when considered in the light of other evidence which you believe.
This instruction is derived from Eighth Circuit Instruction 1.05 and Ninth Circuit Instruction 1.07.