Wayne County Circuit Judge Vera Massey Jones said Tuesday she was convinced Steven Nicholson held his 13-month-old son's face underwater to stop his crying on Oct. 19, The Detroit News reported.
"I don't believe he intended to kill Jonathon," Jones said. "He was overcome by the stresses of being a single parent and he just wanted him to be quiet."
After realizing the boy was dead, Jones said, Nicholson deliberately drowned 15-month-old Ella Stafford to make it appear the two accidentally died playing in the bathtub while he slept.
The toddlers were Nicholson's children by two different mothers.
Defense lawyer William Winters III said he would appeal.
His client waived his right to a jury trial, Winters said, because of fears jurors would be emotionally compromised by graphic evidence photos, including many of the severely scalded bodies.
Jones deliberated for more than 3 hours before finding Nicholson guilty of first-degree premeditated murder, felony murder and first-degree child abuse for the girl's death.
She found him guilty of second-degree murder for the death of the boy.