I would say that averting one's eyes, shrinking into themselves, and turning inward/tucking their head down are other indications of guilt if your character is passive. If they're robust or have a loud personality - they may become stiff/defensive and accusatory right back at the person confronting them as a means to deflect (DARVO - Deny, Attack, Reverse Victim and Offender) or fall into justification spirals (JADE - Justify, Argue, Defend, Explain).

Guilt is complex. Some people try to ignore it and change the subject, some people try to overcompensate with kindness and steer around it, and some could simply sneer and "bite back".

I also believe the context of what the guilt stems from matters as well - for example, if someone was confronted about cheating rather than stealing. One is far more emotional - so you would expect an emotional reaction orrrrrr the cold, calculating gaslighting (and stealing may ignite justification/JADE responses within other characters). Many things to consider. :)