8th Cir. Model Jury Instr. (Criminal) 3.04

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 all of what a witness said, or only part of it, or none of it.

In deciding what testimony to believe, consider the witness' intelligence, the opportunity the witness had to have seen or heard the things testified about, the witness' memory, any motives that witness may have for testifying a certain way, the manner of the witness while testifying, whether that witness said something different at an earlier time,1 the general reasonableness of the testimony, and the extent to which the testimony is consistent with any evidence that you believe.

[In deciding whether or not to believe a witness, keep in mind that people sometimes hear or see things differently and sometimes forget things. You need to consider therefore whether a contradiction is an innocent misrecollection or lapse of memory or an intentional falsehood, and that may depend on whether it has to do with an important fact or only a small detail.]

[You should judge the testimony of the defendant in the same manner as you judge the testimony of any other witness.]2