While this seems a rather fanciful theory on the individual level (it's hard to imagine a police officer letting someone off a significant crime simply because they were a woman) there is a broader point about social expectations. Another consequence of men's "chivalric" values is that they might think women incapable of committing many crimes (temperamentally or physically) and therefore not seriously consider their guilt. In terms of punishment, judges and magistrates (again predominantly male) may take pleas for mitigation more seriously when the offender is female.