A Salt Lake woman has been cleared of charges that she negligently caused the death of her infant son last year.

Dearwin "Dee" Boyd was charged with negligent homicide in the Oct. 1 death of Terry Dean Boyd, 4 months.A witness said he found the baby in a crib with a plastic bag over its head. The witness said the mother was the last person to be with the infant.

When police came, they recovered a plastic bag from a counter, and an autopsy determined that the child's death was consistent with suffocation with a plastic bag.

But some blood found on the plastic bag does not match the child's blood, making it difficult to prove the bag was on the baby at the time of death, said Salt Lake County deputy attorney Rodwicke Ybarra.

Ybarra asked 3rd Circuit Judge Paul Grant on Monday morning to dismiss the charge "in the interest of justice."