Massachusetts ? A man who gave a baby boy and his 2-year-old sister arsenic-based weed killer instead of water at a cookout went on trial Monday, charged with involuntary manslaughter in the infant’s death.

Four-month-old Benjamin Glynn died in 2003 and his 2-year-old sister, Morgan, became seriously ill.

Prosecutor Gerald Shea said Constantine Pitsas, 77, either ignored or didn’t see the warning label attached to the handle of the one-gallon plastic jug that said “arsenical” and “total weed killer.”

But Pitsas’ lawyer, James O’Shea, said Benjamin Glynn’s death and the injuries to his sister were “a tragic accident.”

O’Shea said the label on the jug’s handle was so inconspicuous it was not noticed by the children’s father or a nurse who handled the bottle when it was taken to the hospital emergency room where the children were taken.

Pitsas waived his right to a jury trial and chose instead a trial before a judge.