An aspiring forensic scientist successfully busted a thieving hall monitor at her Long Island high school by setting up a surveillance camera and catching her in the act.

Tiana Rapp, 17, a senior at Newfield HS in Selden, began noticing that money was being lifted from her gym class locker weeks ago.

She and a pal set up a small video camera and they said they saw hall monitor Linda Cubano, 54, open the locker Monday and rummage through its contents.

“It felt good to do something about it,” Rapp said yesterday.