Robyn was the two and one-half-year-old son of David and Ginger Twitchell (D). Robyn died from peritonitis caused by the perforation of his bowel from an anomaly called Meckel's diverticulum which could be corrected with a high success rate by surgery. Ds believed in healing by spiritual treatment. During Robyn's five-day illness from Friday, April 4, through Tuesday, April 8, they retained a Christian Science practitioner, a Christian Science nurse, and consulted with Nathan Talbot, a Church authority who gave advice to Ds. D read a church publication concerning the legal rights and obligations of Christian Scientists in Massachusetts. That publication quoted a portion of G. L. c. 273, § 1, as then amended, which, at least in the context of the crimes described in that section, accepted remedial treatment by spiritual means alone as satisfying any parental obligation not to neglect a child or to provide a child with physical care. The intensity of Robyn's distress ebbed and flowed, perhaps causing his parents to believe that prayer would lead to the healing of the illness. Robyn died. Ds were charged with involuntary manslaughter. Ds argued that the spiritual treatment provision in G.L. c. 273, section 1 of the Commonwealth code protected them from any criminal liability for the death of their son. Ds contend that they had no fair warning that the use of their spiritual treatment could form the basis for a manslaughter prosecution based on an opinion of the State Attorney General that was relied upon in the church publication. The trial court refused to instruct that Ds reasonably believed they could rely on spiritual treatment to avoid criminal liability. Ds appealed.