So we often point to recent statistics (in which reported female perpetration is rising) to dispel the myth that men are almost always the ones engaging in all sorts of criminal behavior. Here's something you can add to that argument: female perpetration is consistently underreported because people have a really hard time believing it. So what you see in the statistics is the very minimum, in reality the percentage will be even higher.

In the article linked below, one woman killed child after child over multiple years. People actually preferred to make up a genetic syndrome, the "Sudden Infant Death Syndrome", rather than looking at obvious signs that she was the killer. It took over 30 years for this case to come to light. If people have this much of a hard time believing that women can do bad things, to the extent that they'd rather spend thousands of dollars on a phony scientific theory as rationalization - then plenty of cases have never come to light. These cases never ended up in the statistics, or if they did, a man was falsely determined to be the perpetrator.

In fact, the people who claim that "men are always the bad guys" and then point to statistics, are the ones keeping the stereotypes alive that bias those statistics.

http://www.newyorker.com/online/blogs/newsdesk/2013/02/did-a-mass-murderer-in-waiting-go-undetected-because-she-was-a-woman.html?currentPage=all?currentPage=all