  We consider a Gelfand-Pinsker discrete memoryless channel (DMC) model and
provide a strong converse for its capacity. The strong converse is then used to
obtain an upper bound on the reliability function. Instrumental in our proofs
is a new technical lemma which provides an upper bound for the rate of codes
with codewords that are conditionally typical over large message dependent
subsets of a typical set of state sequences. This technical result is a
nonstraightforward analog of a known result for a DMC without states that
provides an upper bound on the rate of a good code with codewords of a fixed
type (to be found in, for instance, the Csiszar-Korner book).
