SAN DIEGO -- A 21-year-old Mira Mesa woman who tried to drown her son seven months after attempting to fatally stab the toddler's father was sentenced Friday to seven years in state prison.

Maria Danielle Preshaw, 21, pleaded guilty June 11 to attempted murder.

Defense attorney Steve Wadler told Judge Charles Gill that "significant" mental health issues, including drug addiction, contributed to Preshaw's actions against her son and the child's father.

Wadler said Preshaw has taken advantage of drug and mental health counseling while in custody so she can become a productive member of society when she gets out of prison.

Preshaw was deemed mentally incompetent to stand trial in February 2007 and sent to Patton State Hospital.

Six months ago, the defendant was found competent and sent back to San Diego to face two counts of attempted murder and one count of felony child abuse.

The second attempted murder charge and the child abuse count were dismissed as a result of Preshaw's change of plea.

San Diego police Detective Mark Anning said in an affidavit filed in support of a search warrant that paramedics received a call about 12:15 p.m. on Oct. 12, 2006, regarding a possible drowning victim at 10934 Camino Ruiz.

Two paramedics who responded to the scene found 2-year-old David Hernandez lying on a lounge chair next to an outdoor pool. When paramedics asked the mother how the child ended up in the pool, all she would say is that she placed him there, Anning wrote.

Later, at Rady Children's Hospital, Preshaw told San Diego police Officer Mike Tracey that she put the child in the pool with the intent to kill him, according to the affidavit.

The young mother told Tracey and Anning that the toddler floundered in the water for several minutes, then lay still. She said that when she thought her child was dead, she went for help, according to the affidavit.

A background check on Preshaw revealed that on two occasions in 2006, she was arrested on suspicion of being under the influence of a controlled substance, according to the affidavit.

Deputy District Attorney Matthew Greco said the motive for the attempt on the 2-year-old's life was related to Preshaw's attempted murder of the child's father, Alex Hernandez, with a knife on March 6, 2006.

The boy suffered no lasting injuries and has made a "full recovery," Greco told the judge Friday.