HAVERHILL, N.H. – A Vermont teen-ager already serving life in prison for killing two Dartmouth College professors will be sentenced Wednesday for his role in planning the crimes.

Robert Tulloch, 19, pleaded guilty last month to two counts of first-degree murder in the January 2001 stabbing deaths of Half and Susanne Zantop.

He also pleaded guilty to conspiracy to commit murder, but sentencing on the lesser charge was delayed while prosecutors worked out an agreement that ensures he cannot profit from telling his story, Senior Assistant Attorney General Kelly Ayotte said Tuesday.

James Parker, Tulloch’s partner in the crime, agreed to similar restrictions.

“The agreement doesn’t prohibit him from speaking about the crimes. It prohibits him from gaining any financial profit from having murdered the Zantops,” Ayotte said.

Tulloch’s lawyer could not be reached for comment.

The maximum sentence for murder conspiracy is 30 years. Prosecutors brought the charge based on information provided by Parker, who is serving at least 25 years in prison for helping his friend kill the couple.

Parker, 18, told prosecutors that he and Tulloch were bored with their hometown of Chelsea, Vt., and planned to raise $10,000 to move to Australia. After months spent devising a plan, they decided to kill people and steal their ATM cards and personal identification numbers. They tried four other homes chosen at random before gaining admission to the Zantops’ house in Hanover.

At one Vermont house, the teen-agers cut the telephone lines and Parker hid around the corner while Tulloch knocked on the door. However, the homeowner refused to let Tulloch inside.

At the Zantops’, the teen-agers posed as students conducting an environmental survey. Half Zantop, an environmental sciences professor, sat them down in his study, where the teens stabbed the couple after getting a peek at a large sum of cash in Half’s wallet.

Fingerprints on a knife sheath they left in the Zantops’ home linked the teen-agers to the crime. They fled Chelsea after being interviewed and fingerprinted, and were hitchhiking west when they were arrested at an Indiana truck stop several weeks after the murders.