A driver was arrested and charged with involuntary manslaughter after a head-on collision that killed the other driver. The prosecution claimed that the driver fell asleep while driving and drove into oncoming traffic. At trial, the prosecution called a witness to testify. The witness testified that she was visiting with the driver the morning of the collision when the driver told her he had not gotten any sleep the night before because of a terrible migraine headache. The driver objected to the witness's testimony.

The court should rule that the witness's testimony is