(CNN) -- An Iowa mother was sentenced to life without parole Tuesday for slitting her 2-year-old son's throat and leaving him to die near a remote pond in October 2008, a prosecutor said.
Michelle Kehoe, 36, also received 25 years on one count of attempted murder for slashing her older son's throat. She left both children outside the family van before attempting to kill herself.
The 7-year-old survived and provided key testimony against his mother, whose attorneys argued that she believed she was trying to save her sons from a life of suffering when she cut their throats and her own.
A jury rejected her insanity defense and convicted her of first-degree murder, attempted murder and child endangerment on November 4.
Kehoe also received a 10-year sentence for child endangerment for the injuries she inflicted on her older son, who survived for the night locked inside the family van, Buchanan County Attorney Allan Vander Hart said.
Against the wishes of Kehoe's husband, Judge Bruce Zager also granted an extension of the prosecution's request for a no-contact order, which prohibits Kehoe from contacting her surviving son or anyone with whom he lives.
Kehoe's son lives with her husband, Gene Kehoe, who regularly visited his wife until the order went into effect last April. The judge's decision to continue the no-contact order, which includes written contact, will remain in effect for five years, and extends to father and son.
"When [the victim's] therapist tells us he is ready and it might be beneficial, then that's the time to revisit the no contact order. He's pretty fragile right now," Vander Hart said.
Prosecutors countered that Kehoe methodically planned to kill her sons and herself, but botched it. The detailed planning showed she was not legally insane, Iowa Attorney General Andrew Prosser said.
Kehoe began planning the attack the previous month, buying the knife and the duct tape, according to testimony. She told her husband she was taking the boys to visit her mother at a nursing home.
Police found a handwritten note laying out details of the attack that Kehoe admitted to writing to support the story she initially told police.
The note said a man broke into the car when the family stopped at a gas station and forced them to the area where the van was found. In the note, Kehoe said she tried to fight him off with pepper spray, but he knocked her unconscious.
Kehoe's lawyer, Andrea Dryer, asked the court to run the sentences concurrently on account of her extreme mental illness.
The judge sentenced Kehoe consecutively for first-degree murder and attempted murder and concurrently on attempted murder and child endangerment so that the sentences would represent the two boys.
"I asked for consecutive time because there were two victims and because of the extensive planning and premeditation of these crimes," Vander Hart said.