text: back to the future confusion? in the 2nd movie of the bttf trilogy, marty and doc try to stop martys son from committing a crime, but how can they change it from happening, if its in the future not the present doc went further into the future to see marty's son commit a crime, then went back a few days (with marty) before the crime happened. you see, if the crime didn't happen yet, it can be changed. i don't know if that answered your question or not. basically, as long as the event hasn't physically and chronologically happened yet, it can be changed.