In a deal with prosecutors, Julianne McCrery, 42, pleaded guilty to second-degree murder in the death of her son, Camden Hughes.
She is expected to be to be sentenced to 45 years to life in prison on Jan. 13, 2012.
After her arrest, McCrery told police she drove cross-country from Irving, Texas to Maine to buy castor beans to use in committing suicide, and spent the drive thinking of ways to kill her young son, Senior Assistant Attorney General Susan Morrell said in court.
"There was no one else in her family she believed was fit to raise him if she were dead and she did not think he should be raised by social services," Morrell said.
But Morrell also told Rockingham Superior Court Judge Tina Nadeau that investigators believe, after speaking with acquaintances of McCrery in Texas, that she felt "inconvenienced" by having Camden in her life and that she intended to return to Texas without the boy.
Morrell declined to elaborate on that theory after court.
Morrell said McCrery obtained the potentially lethal castor beans at a Maine emporium on May 12, and spent May 13 at Hampton Beach with Camden, checking into the Stone Gable Motel in Hampton that night. Early the next morning she ingested some of the castor beans and gave Camden some cold medication, Morrell said.
"An hour after feeding him the Nyquil, she took all the pillows off the bed and put them on the floor," Morrell said. "She lifted her son and placed him face down on the pillows. She lay on top of him, applying pressure to his body, with one hand over his mouth and smothered him. She said her son struggled, flailing his legs and arms for about three minutes."
McCrery told police it was daybreak when she put her son's body in the back seat of her Toyota Tacoma pick-up truck and covered it with a green blanket.
"She drove for some time," Morrell said, at one point turning onto a dirt road that led to another road in South Berwick, Maine, where she left her son's body in a wooded area not far from the road.
The discovery of Camden's body under a blanket on May 14 launched a nationwide effort to identify him. Even as that effort was under way, McCrery called his Texas elementary school daily to report him absent, saying he had appendicitis.
Morrell said the mystery of Camden's identity and the conviction of his mother might not have occurred but for a coincidence.
Linda Gove was driving to visit her in-laws in South Berwick when she noticed a blue truck, doors open and vacant, on the typically deserted road. She noticed U.S. Navy insignia on the truck. Glancing in her rear-view mirror, Gove noticed a woman, dark hair pulled into a ponytail, emerging from the woods. With her relatives, she went back and made the grim discovery.
Camden died of asphyxiation, according to a medical examiner, who also noted red blotches around his eyes and a bruise on one cheek.
Based on Gove's descriptions, McCrery and her truck were spotted at a Massachusetts truck stop. Morrell said when she was told about the effort to identify the little boy found dead in Maine, McCrery told a police officer, "Yes, that's my boy."
When Judge Nadeau asked McCrery if she was pleading guilty because she is guilty, McCrery answered softly, "Yes I am."
McCrery appeared calm throughout the hearing as she answered the judge's questions, wearing handcuffs shackled to a waist belt. Her father, Claude Hughes and brother, Christopher Hughes, attended the plea hearing but refused to comment, leaving the courthouse stoically.
"Today is really a difficult day for the McCrery and Hughes families," Morrell said outside court. "They are mourning the loss of Camden and struggling with how he died, at the hands of his mother."
"Today, we have justice for Camden," Morrell said.
Texas public records show that McCrery was arrested at least twice on prostitution charges and once for possession with intent to distribute drugs. In 2009, she was sentenced to one year in prison for a misdemeanor conviction of prostitution. In 2004, she was sentenced to three years of probation for a felony conviction of possession of a controlled substance.
Law enforcement authorities and friends have portrayed McCrery as a loving but troubled mother whose mood swings often prompted her to take lengthy road trips.
A lawyer who represented her at a brief court appearance in Massachusetts has said he got the impression from McCrery that her intent was to take her son's life and then kill herself. But Morrell said text messages to a new boyfriend in Texas that McCrery sent from the Chelmsford rest area implied she thought otherwise.
"That she maintained contact with the school and offered an excuse for Camden's absence suggests she intended to return to Texas," Morrell said.