I believe the answer is that negligence per se does not actually involve application of the criminal statute.  Instead, the common law takes into account the legislative judgment about duty and reasonable care in the particular circumstances and employs that judgment in the tort action.  Indeed, courts have held that the legislative judgment can still be employed even if the criminal statute was not actually enacted due to some missing formality.  The theory, it seems, is that the best evidence of community standards of reasonable care in particular situations is the legislature's judgment, which represents the community as a whole, rather than a single judge or jury.  This theory also leads to the conclusion that the breach of the statute/regulation should be conclusive, non-rebuttable evidence of negligence.  But the standard of persuasion on breach of the standard of reasonable care (borrowed from the criminal statute) is the usual civil one: preponderance of the evidence.

 

The contrary thesis, strongly held in England and Canada, at least, is that breach of the criminal statute should not be conclusive evidence of negligence, or perhaps any evidence: that, if the legislature had desired that result, it could/would/should have said so, and thus that the civil law's using breach of the statute as evidence of negligence is actually contrary to the legislature's intent, or at least relying on speculative legislative intent.

 

Many courts in the USA, and a growing number, seem to take the middle ground: breach of the statute is some evidence of negligence or perhaps even creates a rebuttable presumption of negligence, but it is not conclusive evidence of negligence.