SELMA, Ala. (AP) _ A judge rejected a jury's recommendation and sentenced a former state trooper to the electric chair in the slaying of his trooper girlfriend because the killing was a planned execution.

Prosecutors said Elizabeth Cobb, 31, was fatally shot in a plot by Joe Duncan to collect $350,000 in life insurance benefits.

The killing was a ''premeditated, diabolic, planned execution,'' Dallas County Circuit Judge J.C. Norton said Tuesday at the hearing where he ordered that Duncan be executed instead of serving a life sentence.

Duncan, whose attorneys said they would seek a new trial, told the judge at the hearing that he did not kill Miss Cobb and would join her in heaven to be judged again.

The judge said his assessment of Duncan's guilt stemmed from videotaped interrogations during which Duncan initially denied any knowledge of the Oct. 11 slaying but later conceded he discovered Miss Cobb's body.

Norton said Duncan was ''convicted out of his own mouth.''

Duncan told investigators that he and Miss Cobb, 31, bought the insurance policies while planning to be married.

The slain trooper's body was found Oct. 12 seated in her patrol car behind a rural church. Her service revolver, ticket book and keys were missing and have never been located.

The judge rejected the jury's recommendation, by a 10-2 vote last month, that Duncan be given a sentence of life in prison without parole. The jury had found Duncan guilty of two counts of capital murder earlier in the month.