Parents can legally eavesdrop on young children if they reasonably believe it would be in the child's best interest, the state's highest court ruled Tuesday, establishing an exception to New York law against wiretaps without the consent of at least one person on a call.

The 4-3 ruling by the Court of Appeals involved a cellphone recording of a man threatening to beat the 5-year-old son of his live-in girlfriend. The boy's father recorded the conversation.

"The father had a good faith, objectively reasonable basis to believe that it was necessary for the welfare of his son to record the violent conversation he found himself listening to," Judge Eugene Fahey wrote for the majority. He cautioned that the ruling shouldn't be interpreted as a way to avoid criminal liability for wiretaps "when a parent acts in bad faith."

The live-in boyfriend, Anthony Badalamenti, was later convicted of child endangerment, assault and weapon possession. His attorney challenged the tape as inadmissible evidence from illegal eavesdropping.

Fahey cautioned that courts must consider the age and maturity of the child in considering parental eavesdropping. He didn't specify an age. A key question "is whether the child is capable of formulating well-reasoned judgments of his or her own," he wrote.

Chief Judge Janet DiFiore and Judges Eugene Pigott Jr. and Michael Garcia agreed with Fahey.

In a dissent, Judge Leslie Stein wrote that the issue raises many policy concerns that should be left to the Legislature, with implications for divorce and custody disputes, criminal proceedings against the minor or others, juvenile delinquency and any other dispute within families.

Even in this case, the father didn't notify authorities or share the tape until after Badalamenti and the boy's mother were arrested months later when neighbors heard screaming and crying and called police, Stein wrote. The majority's ruling fails to answer whether a parent can eavesdrop over the explicit refusal of an older child who's talking to his or her other parent, she wrote.

Judges Jenny Rivera and Sheila Abdus-Salaam joined Stein's dissent.

Calls to Nassau County prosecutors and Badalamenti's attorney were not immediately returned.

The New York court said this "vicarious consent" doctrine was adopted by a federal court in Utah in 1993 and the federal appeals court in Cincinnati in 2008.