In criminal law, when is "common law" used, when is the "model penal code" used?

[iomar]

common law = precedent

It's used in every case

The basic routine for researching a case goes like this:

1--define the crime
2--define the specific section of the US code that has been violated
3--research cases indexed by that code for prior interpretations likely to be used

Step 2 is a research of statutory law.
Step 3 is a research of common law.

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The second answer is wrong.

There's not a single case in any law library in America that references English common law. Courts are restricted to American statutes and American precedent.