That's not the whole story. The student's honor is considered good enough that we shouldn't spend time locking things down, but at least when I interacted more with undergraduates here, Caltech had an investigation process for undergraduate academic dishonesty that was student-run and utterly dysfunctional, apparently involving scenes that would bring to mind the Spanish Inquisition, complete with 2am interrogations and insistence on confessions.
I was told of severe disciplinary actions for accusations that were ridiculous when students would not confess, and an administration that stood behind the decisions of students who judged other students more on their opinions than anything else. One student, for example, was apparently expelled for an instance of claimed cheating that would have involved him running back and forth on campus at the speed of a competitive athlete. He quietly returned a short time later, and was also admitted here as a graduate student; there were rumors of legal threats and a settlement.
At least when I was hearing more about such things, essentially, Caltech placed tremendous trust in students who were well-liked by particular people, and treated those who were disliked very poorly.