SJC: Medical evidence needed to prove lack of capacity to sign contract

The state’s highest court ruled today that a person who claims they lacked the capacity to enter into a contract must provide medical evidence to prove it.

The Supreme Judicial Court ruled in the case of a Woburn woman who settled a dispute over ownership of the family home but claimed that the 2006 agreement was unenforceable because she had experienced a “mental breakdown” during the mediation.

The woman had testified that she was “out of control emotionally” during the mediation and “she was not thinking rationally on that day.” Her husband also testified that she was “having a breakdown.” No medical experts testified about her condition.


The court, in an opinion written by Justice Fernande R.V. Duffly, said it had never before addressed whether medical evidence was necessary to prove someone did not have the capacity to sign a contract.

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It said that in prior cases it had considered, “evidence of mental illness or defect has been presented consistently through medical evidence, including the testimony of physicians and mental health providers or experts, in addition to lay testimony. Moreover, in other contexts, we have held that a lay witness is not competent to give an opinion as to mental condition.”

“Expanding on this analysis, we conclude that medical evidence is necessary to establish that a person lacked the capacity to contract due to the existence of a mental condition,” the court said in the ruling in the case, Sparrow v. Demonico.