An NYPD cop accused of paying a Twitter user for kiddy porn also engaged in video sex chats with young girls and had over 400 photos of child sexual abuse stored on a laptop found in his home, federal prosecutors alleged at the start of his trial Tuesday.

Timothy Martinez,43, was after “explicit images of underage girls and children” — and compiled a horrifying collection on the computer seized during a 2019 raid, prosecutor William Campos said during his opening statement in Brooklyn federal court.

“Martinez engaged in live video sex chats with underage girls and had them display their bodies — including their breasts and vaginas — and masturbate,” Campos told jurors.

But Peter Brill, defense attorney for the veteran cop and Army reservist, sought to muddy the waters by claiming that the sickening images found on the laptop could have come from any one of the dozens — if not hundreds — of soldiers with whom Martinez shared the computer during stints at military bases in Iraq, Afghanistan and Romania.

“It was a general-use laptop used by anyone Martinez shared a base with,” Brill told the jury.

“These images are disgusting … but this case is about whether Tim knowingly possessed child pornography.”

It was a sharp opening salvo in a long-awaited trial that will determine whether Martinez, a Staten Island resident who was arrested in February 2020, will go to jail for allegedly paying a Twitter user for explicit photos and videos of child pornography. Martinez allegedly believed the owner of that account was a minor.

Investigators from the Department of Homeland Security allegedly linked Martinez to the Twitter account that paid the other user, according to an affidavit filed in federal court.

On Tuesday, Martinez wore a Navy blue suit, blue shirt and black tie as he listened to the attorneys trade barbs.

Campos, the federal prosecutor, also said investigators have copies of Skype sex chats that Martinez allegedly had with two unnamed girls.

He met one, a 13-year-old girl, online and allegedly manipulated her into “displaying her naked body for his pleasure,” Campos said.

Brill shot back that the girls Martinez allegedly chatted with never actually saw him — only his picture, which was his Skype account’s avatar.

“The women will say they recognize him but they recognize his picture,” Brill said. “They have absolutely no idea who they talked to.”

Authorities have charged Martinez with possession of child pornography.

He was released on a $150,000 bond on in February 2020, according to SILive.com. He is listed as being on paid extended leave from the department.