WHITE PLAINS, N.Y. (CBSNewYork/AP) — Lacey Spears, the mother accused of poisoning her 5-year-old son with a lethal dose of salt, was convicted of murder Monday.

As CBS2’s Lou Young reported, a White Plains jury returned a unanimous guilty verdict, and with that, Spears, 27, went from defendant to convicted killer. She looked away from the jury dejectedly as her sister, Rebecca, and father, Terry Hogan, comforted each other in the court gallery.

Spears was then led out of the courtroom in handcuffs.

The jury deliberated for more than two days before finding Spears guilty of second-degree depraved murder, WCBS 880’s Marla Diamond reported.

Jurors seemed to struggle with the definition of “depraved indifference,” asking the judge to repeat it three times. After the third request, they came back quickly with their verdict.

Meanwhile, the defense has continued to claim she is innocent, and has vowed to appeal.

“It’s still a mystery as to what caused Garnett’s death,” defense attorney Stephen Riebling said.

But the Westchester County District Attorney’s office and now the jury beg to differ. Garnett spears died from a massive concentration of salt introduced into a feeding tube his mother kept in him from a treatment he had in infancy.

The state claims she kept him sick for sympathy.

An alternate juror says video of mother and son just after one of the poisoning incidents convinced him. It was footage so disturbing the DA won’t release it publicly.

The video showed Spears taking her son into a hospital bathroom with a connector tube and the boy suffering afterward.

“The way she came out of the bathroom, sat on the bed with him and just watched him – you know, kind of like if you put, like, something in the microwave, put it on two minutes, and just sit there waiting for something to happen that you know is going to happen eventually,” said alternate juror Andrew DiGiacomo.

When asked if it seemed like he was observing a murder, DiGiacomo said yes.

Prosecutors said that Spears fed her son large amounts of salt through a gastrointestinal feeding tube, causing brain swelling, seizures and death. They believe she administered the salt at their home in Rockland County, as well as in his room at Nyack Hospital in Nyack after he was admitted for seizures. He died Jan. 23, 2014, after being transferred to Westchester County Medical Center in Valhalla.

Garnett Spears (credit: Facebook)

Garnett Spears (credit: Facebook)

The boy had a special feeding tube in his abdomen that was left over from an illness he had in infancy, which provided Spears with the ability to sicken her son at their home in Chestnut Ridge and then fatally poison him during subsequent hospital stays, prosecutors said.

Prosecutors said Spears purposely sickened the boy to gain attention on social media and called her “a calculated child killer.”

Lacey Spears' father and sister embrace after the guilty verdict was read in court on March 2, 2015, in White Plains, N.Y. (credit: Marla Diamond/WCBS 880)

Lacey Spears’ father and sister, shown here on a courtroom monitor, embrace after the guilty verdict was read March 2, 2015, in White Plains, N.Y. (credit: Marla Diamond/WCBS 880)

A feeding bag found in Spears’ apartment had the equivalent of 69 McDonald’s salt packets in it, a forensic toxicologist testified. The defense implied the bag could have been tampered with.

A friend of Spears told the jurors that after Garnett died, Spears asked her “to go to her house and get a feeding bag in the middle of the room and throw it away and not tell anybody.”

There were no defense witnesses, but Spears’ lawyers portrayed her as a doting mother and extensively cross-examined several prosecution witnesses, attempting to show there could have been other causes for the boy’s death.

Riebling argued Garnett was allowed to become dehydrated — then was given a salty IV fluid. He also tried to question the motive lain out by prosecutors and convince jurors that police botched the investigation.

Riebling also attempted to cast doubt on the county medical examiner’s office’s finding that high salt was the cause of Garnett’s death.

Experts say the case fit the profile of Munchausen syndrome by proxy, an insanity defense her lawyers did not purse, saying there was enough reasonable doubt for an acquittal. Munchausen by proxy is a disorder in which caretakers purposely harm children and then bask in the attention and sympathy.

As Spears moved around the country — Alabama, Florida and eventually New York State — she kept friends updated on her son’s frequent hospitalizations with photos and musings on Facebook, Twitter, MySpace and a blog.

Detectives conducted 150 interviews in five states to retrace their life together as mother and son, killer and victim.

The jury asked if mental illness could be considered as a mitigating factor. The judge said no, since no evidence of mental illness had been introduced at trial.

As CBS2’s Weijia Jiang reported, defense attorneys said they did not regret the fact that they never brought up mental illness.

“Absolutely not,” said defense attorney David Sachs. “As the judge said, there’s no evidence of mental illness in this case. Our client fully intends to appeal and to do that as soon as legally possible.

And the District Attorney sees no mitigating factors in this case.

“At sentencing, my office will be asking the court to sentence Ms. Spears to the maximum sentence allowed under law,” said Westchester County DA Janet DiFiore.

The maximum sentence is 25 years to life in prison. DiFiore said she will ask for life.

“In the end, this was not a close case,” DiFiore said. “It was an overwhelming body of evidence that convicted this woman.”

And when asked if Garnett Spears got justice with his mother’s conviction, Ramapo Police Chief Peter Brower said, “I believe he did.”

Spears is set to be sentenced on April 8.

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