In To Kill a Mockingbird, of what crime is Tom Robinson found guilty?

In chapter 14, Scout asks her father what rape is: "He sighed, and said rape was the carnal knowledge of a female by force and without consent" (135). She asks this because in chapter 12, when she goes to Calpurnia's church, she had asked Cal what Tom Robinson was in jail for. When Calpurnia told her it was for rape, she told Scout to get the definition from her father. The court case is detailed in chapters 17-20. Bob and Mayella Ewell claim that while Tom Robinson was helping Mayella with some chores one day, he violently raped her. There are no other eye witnesses to vouch for what they say, though. There is also no solid evidence to support their claims--not even a doctor's examination to draw evidence from because Ewell didn't think it was necessary. He didn't think it was necessary because the rape charge is clearly fiction. Unfortunately, in Maycomb, Alabama in the 1930s, a criminal charge by a white man against a black one winds up in court, gets tried without evidence or witnesses, and Tom is convicted of rape as charged.