Intro to the Federal Rules of Evidence - 44

6. Contradictory Facts
The purpose of impeachment by contradiction may be included in “for other purposes” under 404 (b).

Ethics rules are particularly important here. The cross examiner cannot suggest a contradictory fact unless he has a good-faith basis for doing so and can prove the fact when required to do so.
If the witness does not admit it, the cross-examiner must prove up the non-collateral facts with extrinsic evidence.

7. Mental or Sensory Perception Problems
There is no federal rule on this type of impeachment but plenty of cases.
A witness may be impeached by showing that he had no knowledge of the facts to which he testified, or that his faculties of perception and recollection were so impaired as to make it doubtful that he could have perceived those facts. Such a showing can be made either on cross examination or by the use of extrinsic evidence.