SAN DIEGO -- A Washington state couple charged with murder in the medication overdose death of their 6-month-old son, who died while the family was vacationing in San Diego, pleaded guilty Monday to involuntary manslaughter and child abuse charges.

Lorrie and Thomas Boettger, both 39, admitted their guilt in a hearing before Judge Michael Wellington.

Lorrie Boettger pleaded guilty to involuntary manslaughter and will be sentenced to two years in state prison on July 25. Her husband pleaded guilty to felony child abuse causing great bodily injury and will also be sentenced to a two-year prison term on the same date.

Both defendants have been in jail since their March 2007 arrests. They could have faced up to 15 years to life behind bars for the Oct. 25, 2006, death of Thomas Boettger Jr., prosecutors said

"This plea reflects that the parents are criminally responsible for the death of their young son," said Deputy District Attorney Matthew Greco.

Medical Examiner Investigator James Ramirez testified last September that Thomas Boettger told him that he had diagnosed his son with gastric upset and put over-the-counter medications in the baby's bottle to help him sleep.

The father said he had given the infant half-crushed tablets of Unisom, Zantac and Benadryl, and also said that he had administered the medications with liquid in a syringe for months, the investigator testified.

San Diego police Officer Christopher Luth, one of the first officers on the scene, testified that Thomas Boettger told him that he was an emergency medical technician and was performing CPR on his son when authorities arrived.

Luth said the father told him that the child was colicky and had not been sleeping.

The officer said Thomas Boettger directed him to a bathroom, where he found packages of sleeping pills and antihistamine.

Defense attorney Merle Scheidewind said the parents were giving their son medications that they thought would help.