How are procedural defenses different from substantive defenses?

The difference between these two is that a substantive
defense argues that the defendant did not actually commit the act alleged against him or
her while a procedural defense simply says that the defendant is not legally liable,
regardless of whether he or she commited the alleged
act.

In a procedural defense, the defense does not
necessarily claim it did not commit the alleged act.  Instead, it argues that it is not
legally liable.  An example of this would be the defense of entrapment.  In this
defense, the defendant claims that they would not have done the act but for the actions
of the government.  In such a case, the defendant is admitting that they actually
committed the act, but is claiming that they are not liable because of misconduct on the
part of the government.

So, a substantive defense says "I
didn't do it" while a procedural defense says "Regardless of whether I did it, you can't
find me guilty because..."