One defense that clients frequently bring up in Criminal Defense cases is Ignorance or mistake as to law or fact. In terms of mistake of law, it is an almost universal rule in the law that ignorance of the law is not and cannot be a defense. Specifically, it is not a defense to speeding on a highway that you did not know that speeding was a crime in the state of Pennsylvania if the roadway has speed limit signs properly posted along the highway.learn about Murder charges Additionally, it is also not a defense in regards to ignorance of the law if an accused believes that it is legal to possess marijuana in the commonwealth of Pennsylvania when it is not. However, under Pennsylvania law, mistake as to a fact can be a defense. Specifically, it can be a defense in a speeding case if there are no signs on the highway explaining what the speed limit is and the driver mistakenly believes that the speed limit is 75 miles per hour when it is really 65 miles per hour.

In terms of Criminal Defense, the law dealing with Ignorance or mistake can be found in the Pennsylvania Crimes Code under Title 18 and in section 304. That law states: Ignorance or a mistake to a matter of fact, for which there is reasonable explanation or excuse, is a defense to criminal charges if there are certain factors that are met.  when is prosecution barred Specifically, (1) the ignorance or mistake negatives the intent that the government is required to establish as part of the criminal charge; or under Pennsylvania law, the mistake of fact constitutes a defense. What would be another example of where mistake of fact could negate criminal charges? The defendant picks up an aluminum bat when he mistakenly believes it is a whiffle bat and strikes the victim in his head with the bat. This mistake, if believed, would negate the intent requirement for assault charges.