A “Law & Order” star will get a chance at some real-life justice when she takes the stand against her accused stalker, whose federal trial starts today in Brooklyn.

“Criminal Intent” star Kathryn Erbe could testify as soon as today against Charles Nagel. The songwriter and musician wannabe from Philadelphia is accused of showing up on a set where Erbe was filming in July 2008 and sending abusive messages online to her, her young daughter and brother over two years.