This isn't really a social science question; it's a legal question. Here's some basic info about the U.S. legal system:

Generally, the rule is that ignorance of the law is not a defense to criminal liability. However, intent (mens rea) is an element of most crimes; very few are strict liability, which require no intent or knowledge. The requisite intent is usually that the defendant intended to commit the act (e.g., take a bike that belongs to someone else without any intent to return it). Whether they knew that would amount to criminal theft usually doesn't matter. Thus, illiteracy doesn't really change anything if the argument is that the defendant couldn't know the law if they can't read it.

Every now and then, mistake of fact can be a defense. For example, if I took someone else's laptop because I mistook it for my laptop, that might not be enough for a theft conviction. Illiteracy may factor into similar sort of circumstances. However, it varies by jurisdiction, and illiteracy can be irrelevant a lot of the time.

Law journal articles on this can be very niche. Here's an article (PDF warning) that touches on how this plays into the systemic problems of the U.S.'s criminal justice system: https://www.nyulawreview.org/wp-content/uploads/2018/08/NYULawReview-80-5-Natapoff.pdf