An admitted drug kingpin testifying for the government in the second trial of alleged rogue Philadelphia cop Malik Snell identified Snell in a federal courtroom yesterday as the cop who robbed him of $40,000 in December 2007.

But Snell's attorney questioned the credibility of drug dealer Ricardo Mc-Kendrick Jr.'s testimony, pointing to a major discrepancy between what he said yesterday and earlier grand-jury testimony.

Snell, 36, an 11-year veteran of the force assigned to the 18th District in West Philadelphia, was fired last year.

Snell's first trial on conspiracy and robbery charges, involving a 2007 Pottstown home-invasion robbery that went awry, ended in a hung jury in October.

Prosecutors later charged Snell with robbing McKendrick and threatening him and another drug dealer, Keino Herring, whom Snell suspected were cooperating with the feds.

McKendrick, who testified for about two hours, said under questioning by prosecutor Kathy Stark that Snell pulled him over in what he thought was an unmarked police car.

Prosecutors say that Snell outfitted a black Dodge Intrepid with blue flashing lights and an airhorn to make it look like an official police car.

McKendrick testified that Snell pulled over his minivan in South Philadelphia, handcuffed him, searched the van and put him into the back of the Intrepid. McKendrick said that at one point, he saw a bulge in the officer's jacket pocket, but did not see a gun.

But McKendrick told a different story when he was asked about it before the grand jury, said defense attorney John McMahon.

McMahon showed McKendrick a copy of his grand-jury testimony in which he said that Snell had a black handgun that had a magazine clip at its bottom, that was either a 9 mm or a 45 mm, and that was "definitely an automatic weapon."

In response to a question from McMahon about whether he had lied to the grand jury, McKendrick said his grand-jury testimony was truthful and to the best of his recollection at the time.

On redirect by Stark, McKendrick said his best recollection today was that he "didn't physically see a gun" on Snell, but only a bulge from the pocket of Snell's windbreaker.

McKendrick also admitted yesterday that he had told investigators that he had been robbed but didn't say how much money was involved because he didn't want to draw attention to himself or his drug deals.

McKendrick and his father were busted by a joint FBI-Philadelphia Police drug task force last April.

Authorities found more than 600 pounds of cocaine with an estimated street value of $28 million inside their South Philadelphia rowhouse.

Both men pleaded guilty to federal drug charges in December and face mandatory minimum sentences of 10 years in federal prison. *