Impeachment
a)    impeachment allowed
b)    improper impeachment is the problem; as a subterfuge for improper purposes
i)    If W testifies to a non-collateral matter on direct, then opponent may impeach on both cross and by extrinsic E.
ii)    If W testifies to a collateral matter on direct, then opponent may impeach on cross, but must take the answer.
iii)    set-ups not allowed:  Setups or “smuggling” –> if W never testifies on direct to the fact to be impeached but cross-ex elicits facst on cross, for the purpose of setting the W up for contradiction, and then seks to contradict the answer by extinsic E
c)    Leaves false impression on direct-ex? On direct, the W doesn’t directly contradict the impeaching E, but testifies about the general s.m. and leaves a false impression of a fact that is inconsistent w/ the impeaching evidence.
i)    Tex  rule  can impeach false impression given on direct (and can use extrinsic E)
ii)    (US) If the cross-ex is rzbly suggested by the direct T, then the impeachment Evidence (extrinsic) may be used.  “Plainly w/in the scope of D’s direct ex.”
iii)    same thing if given not on “direct” but as a nonresponsive answer on cx
d)    for improper setups can use 403 b/c probative value only to setup
e)    calling a witness only to impeach him (impeaching your own W)
i)    607 allows it
ii)    but usually 403 will keep it out
iii)    wait until W put on & says the bad stuff then don’t let him impeach him