Art Modell's Son -- Accused Grave Pisser Suspect Can Shove His Apology

Art Modell's son wants to see the man accused of peeing on his father's grave prosecuted -- and he wants to do so in person ... telling TMZ Sports he will absolutely be in court to stare down the suspect.

David Modell has heard Paul Serbu's claim the incident -- which became a viral video -- was all a prank and that he didn't actually pee on the grave site ... but he's not buying it.

Modell -- who was Ravens President from 2001 to 2004 -- says Serbu must be held accountable, and he's looking forward to a trial.

Serbu's attorney told TMZ his client desperately wants to reach out to the Modell family and apologize -- but he shouldn't hold his breath. David tells us Serbu "shouldn't reach out [to my family]. He should call his attorney."

As for feeling any relief that Serbu was found and charged -- Modell says, "The only misplaced relief here was his."