NEW YORK — It's not clear who got the last laugh Tuesday as the senior CBS news producer accused of trying to extort $2 million from talk show host David Letterman admitted the offence in a plea deal.

A Manhattan judge sentenced Robert "Joe" Halderman to six months in prison after he pled guilty to second-degree grand larceny in the shakedown, which he admitted was payback for Letterman's affair with his live-in girlfriend.

That's a far cry from the possible 15-year prison term Halderman could have received if found guilty of the initial first-degree grand larceny charge.

With credit for good behaviour, Halderman, 51, could be released after four months.

The judge also ordered Halderman to complete 1,000 hours of community service, and remain on probation for 4 1/2 years following his release.

"I had complete faith that a just and appropriate result was inevitable," Letterman said in a statement released by his lawyer, Daniel J. Horwitz.

News of the conclusion of the prosecution was expected to produce a ratings boost for the Tuesday edition of Letterman's Late Show, which is also produced by CBS.

Increased numbers of viewers tuned in after Letterman, 62, used his show Oct. 1 to reveal the extortion plot following Halderman's arrest that day.

Halderman drafted a screenplay treatment that effectively exposed a series of affairs that the married Letterman has had with members of the Late Show staff.

He then tried to "sell" it to Letterman, leaving it in the back of the talk show host's limousine. He asked for and received a cheque for $2 million, but the authorities had been notified and monitored its delivery.

The purported script told of a late-night TV talk show host who had slept with female staff employees. Halderman drafted it after learning that Letterman and his former girlfriend Stephanie Birkitt, 34 — also a Letterman staffer — had continued with an affair she'd earlier promised to abandon.

Letterman admitted to his audience that he had indeed had affairs, saying: "You can't be victimized by criminals."