The Maine Supreme Court has upheld a guilty plea in one of the state’s oldest “cold cases” – the killing of a 4-month-old in 1979.

The death of Nathan Hagar had originally been ruled as sudden infant death Syndrome, an unexplained death considered accidental. That finding held up despite repeated confessions over the decades by Burton Hagar that he had smothered his son with a pillow in the baby’s crib in a Brunswick apartment.

The case remained in limbo because the state cannot try someone who confesses without evidence that a crime was committed. Burton Hagar’s confessions weren’t enough, even those he made, on tape, with state police detectives.

However, in April 2018, nearly 39 years after the baby’s death, prosecutors asked a Cumberland County Superior Court judge to rule that the infant was killed and try Hagar for the crime.

The ruling turned on the concept of corpus delicti, in which the court finds that a crime has been committed. The principle is meant to prevent people from confessing to crimes they didn’t commit, although the confessions often are still admitted as evidence once the court determines a crime was committed.

Prosecutors had determined for nearly 40 years that the infant’s death wasn’t criminal because the cause was accidental. But a former state medical examiner reviewed the case and told Superior Court Justice Thomas Warren last spring that she would reclassify the cause of death to smothering asphyxiation and the manner to murder. In addition, a former Brunswick police officer who had responded on the call in 1979 testified that he saw mucus on a pillow in the baby’s crib, but stopped investigating after the case was reassigned and he learned doctors had determined the baby died of SIDS.

Hagar’s lawyer argued that his client’s confessions – more than a dozen, including to four of Hagar’s former wives, his counselors, psychiatrists and state police detectives – varied on key details and shouldn’t be relied on in pursuing charges.

But Warren ruled that a crime had been committed and Hagar pleaded guilty to manslaughter. A deal called for him to be sentenced to 15 years as he pursued an appeal of the ruling to the state Supreme Court, which decided this week to uphold Warren’s finding.

The top court said it declined to change the state’s corpus delicti standard that says prosecutors must show that a crime has been committed, regardless of confessions. Federal courts and some states now require prosecutors to instead prove the “trustworthiness” of confessions, which Hagar’s lawyer, Verne Paradie, favored, rather than that a crime had been committed.

The ruling noted that prosecutors also asked the Supreme Court to change the standard to one based on the “trustworthiness” of confessions, but the court dismissed those arguments in a footnote, saying justices saw “no reason to abandon” the corpus delicti precedent. Then, the Supreme Court went on to rule that Warren had sufficient evidence to determine that a crime had been committed.

Paradie said he didn’t plan to pursue limited options for further appeal. He said Hagar can pursue a post-conviction review, but that would likely involve a different lawyer.

Hagar has been imprisoned since his arrest in April 2017. Warren took the unusual step in July 2017 of granting him bail, but Hagar was unable to raise the $10,000 cash or $100,000 surety.

A spokesman for the Maine Attorney General’s Office declined comment on the ruling.