United States v. Crawford, 239 F.3d 1086 (9th Cir. 2001)

'A lay witness may testify as to an ultimate issue of fact, so long as the testimony is otherwise admissible. Fed. R.Evid. 704. The lay witness may not, however, testify as to a legal conclusion, such as the correct interpretation of a contract' (at 1090) (citing Evangelista, 777 F.2d at 1398 n.3).