An indictment in Haverhill is the first statement from prosecutors alleging a motive for the Jan. 27 deaths of Half and Susanne Zantop in their Hanover home. But the jury for Robert Tulloch will be asked to consider two theories of first-degree murder that it was "purposeful," with no motive specified, and that it was committed during a robbery, Attorney General Philip McLaughlin said in a statement.
Tulloch, 18, and his best friend, James Parker, 17, both of Chelsea, Vt., were charged with the murders after they were arrested Feb. 19 at a truck stop near New Castle, Ind.
Parker recently pleaded guilty to being an accomplice to second-degree murder in the death of Susanne Zantop and will be sentenced to 25 years to life in prison after he testifies against Tulloch.
Tulloch's lawyer announced last month he would use an insanity defense. His trial is scheduled to start in April in Grafton County Superior Court.
Prosecutors have said they have found no connection between the teens and the German-born professors.
Prosecutors say they found fingerprints and footprints in the Zantops' home that link the teens to the murders. Court documents say two military-style knives stained with the victims' blood were found hidden in Tulloch's bedroom.
Half Zantop, 62, taught earth sciences at Dartmouth, and his wife, Susanne Zantop, 55, was head of the German studies department.
Tulloch still faces an earlier indictment charging him with first-degree murder in both deaths. That indictment did not allege a motive.
McLaughlin announced the new indictment, but he said it would not be made public until Monday. He declined to comment or elaborate on his statement.
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