The prime suspect in the fatal stabbing of Barnard College student Tessa Majors was seen leaving the Harlem offices of his defense lawyers on Thursday, just hours after cops took a DNA sample to try to link him to the high-profile killing.

The 14-year-old boy wore a gray hoodie and gray sweatpants as he walked out of the building that houses the Neighborhood Defender Service of Harlem at 317 Malcolm X Blvd. around 4:45 p.m.

The unidentified teen headed south with a woman in her 30s and an older teen, both wearing street clothes, and were joined by an Asian man in a suit who came running up as a Post reporter approached and began asking questions.

“You better back off. Back off!” the woman said.

The group ignored repeated questions but the woman slapped a recording device out of the reporter’s hand while crossing 125th Street, yelling “Go ahead! You’d better go ahead! Move! F–k!”

She and the two teens hopped into a white SUV that was idling in front of a fire hydrant, then pulled out and traveled east on 125th St.

Earlier in the day, cops took the younger teen into custody in the Bronx and brought him to Harlem’s 26th Precinct station house, where they executed a search warrant and swabbed his cheek for DNA, sources said.

He was released without charges to the custody of his lawyers, NYPD Chief of Detectives Rodney Harrison tweeted.

A 13-year-old boy, who’s charged with second-degree murder as an accomplice Majors’ death during a Dec. 11 robbery in Morningside Park, has allegedly identified the teen as her killer.