  By explicitly representing the reaction times of discrete chemical systems as
the firing times of independent, unit rate Poisson processes, we develop a new
adaptive tau-leaping procedure. The procedure developed is novel in that
accuracy is guaranteed by performing postleap checks. Because the
representation we use separates the randomness of the model from the state of
the system, we are able to perform the postleap checks in such a way that the
statistics of the sample paths generated will not be biased by the rejections
of leaps. Further, since any leap condition is ensured with a probability of
one, the simulation method naturally avoids negative population values
