Police have just released body cam footage showing Sunny Hostin's son being cited for trespassing -- it shows her aggressively arguing with cops on his behalf ... and she pulled out the Harvard defense almost immediately.

In the clip, Sunny and her son, Gabriel Hostin, explain what happened to the officers ... telling them he was on a run along the tracks when he saw a hill and decided to head up it.

She then plays the Harvard card ... telling officers he just graduated from the Ivy League school -- and he's an upstanding citizen who teaches 4th-grade geometry, while she herself is a former federal prosecutor. Basically, my son's a good kid -- can we wrap this up?

Sunny explains they just moved to the area in the last year ... which is why he made the mistake of going onto private property -- he's still new to the area and learning.

Additional body cam video shows the officers approaching Gabriel on the train tracks.

Cops even put Gabriel in handcuffs while he's on the phone with Sunny.

Cops also released a photo of the gate that Gabriel says was open when he was out for the run ... as well as the no trespassing sign he says he didn't see.

As you know ... the heated interaction went down last month, when Gabriel was out for a jog and noticed "a gravel incline that could be used for hill training."

Cops say he was trespassing on active railroad tracks in New York.

"The View" host -- a former federal prosecutor and attorney -- is representing her son in the case.

We broke the story ... Sunny wrote a letter to the D.A., asking them to drop her son's case. She claimed there was no visible "no trespassing" at the incline's entrance, and her son made an "honest mistake" assuming it was an open area.

Gabriel's court appearance is scheduled for July 31.