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The defense for a mother accused of killing her 5-old son with salt and documenting his decline on social media faces an uphill battle in her murder case, according to legal experts.

Lacey Spears, 27, of Scottsville, Kentucky, who presented herself online as a supremely devoted mother, is charged with depraved murder and manslaughter in the death a year ago of Garnett-Paul Spears.

Jury selection began Monday in the case of Spears, who was living in Chestnut Ridge, N.Y., at the time of her son's death. Garnett Spears died at Westchester County Medical Center Jan. 23, 2014, after being hospitalized, first at Nyack Hospital, several days earlier.

Although his mother had for years blogged of his health problems, authorities became suspicious when doctors discovered the alarming sodium level in the child's body, and the Westchester County medical examiner has ruled the death a homicide. Shortly after the boy was hospitalized for the last time in his short life, his mother called a neighbor and asked that she destroy any evidence of feeding tubes within the home, a source close to the case told FoxNews.com.

"This mother was intentionally feeding her child salt at toxic levels," prosecutor Doreen Lloyd said at Spears' arraignment.

"Asking her neighbor to take a feeding bag which contained a high dose of sodium is powerful consciousness of guilt evidence."

— Mark Bederow, criminal defense attorney and former prosecutor

Spears, meanwhile, has denied any wrongdoing through her attorneys.

The boy's sodium levels rose to a dangerous point with no medical explanation, prosecutors said, leading to a swollen brain, seizures and death. They believe his single mother, who was sharing his hospital room at Westchester Medical Center, administered salt through a feeding tube into Garnett's stomach.

All the while, Spears was keeping followers up to date with 28 online postings in the last 11 days of his life, noting his death with, "Garnett the great journeyed onward today at 10:20 a.m." She had tens of thousands of entries over Garnett's lifetime, many about his doctor and hospital visits.

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"My Sweet Angel Is In The Hospital For The 23rd Time," Spears tweeted on Nov. 9, 2009, adding a sad-faced emoticon. "Please Pray He Gets To Come Home Soon."

Jury selection began Monday with a pool of 90 potential jurors on hand at the courthouse. Several told the judge they had seen some of the extensive news coverage of the case.

Mark Bederow, a New York-based criminal defense attorney and former prosecutor, said Spears and her defense team face many challenges due to strong circumstantial evidence incriminating her in the boy's death.

"Her Internet search about the dangers of sodium and the properties of iodized salt provide strong evidence that she knew what could happen to her son and thus exhibited a depraved indifference to human life," Bederow told FoxNews.com.

"Asking her neighbor to take a feeding bag which contained a high dose of sodium is powerful consciousness of guilt evidence," he said.

Prior to his death, the boy had become known as "Garnett the Great" to an online circle who followed reports by his mother. Spears chronicled his many hospital stays and dietary problems on a blog, "Garnett's Journey," subtitled "Healing takes courage, and we all have courage, even if we have to dig a little to find it."

The single mother had moved from the South to live in the quiet "Fellowship Community" in Chestnut Ridge, N.Y. -- a close-knit, rural community about 40 miles north of New York City that cares for the elderly and prides itself on organic farming and other self-sufficient means of living. The legal responsibility for the community is carried by the Rudolf Steiner Fellowship Foundation, Inc., a non-profit licensed by New York state as an adult care facility, according to its website.

In rulings delivered last week, Spears' messages on Facebook, Twitter and MySpace were determined relevant and are likely to be introduced as evidence. Some of the posted photos depict Garnett's declining health, said acting state Supreme Court Justice Robert Neary.

Neary also found that prosecutors can tell jurors about Internet research Spears did on her iPhone into the dangers of sodium in children and the properties of iodized salt.

In addition, the judge said Garnett's hospital records from Alabama, Florida and New York are relevant and "inextricably interwoven into the fabric of this case. They provide a history of the child's medical issues and treatment leading up to his death. They illustrate the defendant's role as custodian and care giver."

Prosecutors believe Spears often lied to doctors about Garnett's health, for example claiming he had celiac disease when he didn't.

Spears' lawyers have not publicly detailed a defense strategy and did not return calls seeking comment. Attorney Stephen Riebling said in July that the defense would focus "on the relevant facts, not fiction."

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Other evidence in the case includes bags used to feed Garnett which prosecutors say have "extraordinary" concentrations of sodium. The prosecution says Spears tried to cover up by asking a friend to take a feeding bag, "get rid of it and don't tell anybody."

The trial apparently will not include any reference to Munchausen by proxy, a disorder in which caretakers purposely but secretly harm children and then enjoy the attention and sympathy they receive. Some experts regard it as a mental illness and a defense to such crimes, while others consider it a motive. Several believe Spears' case fits the syndrome.

Spears' lawyers asked the judge to prohibit any mention of Munchausen and prosecutors said they had no plans to bring it up.

"It is somewhat surprising that the defense would not seek to offer evidence consistent with Munchausen by proxy which might emotionally move a jury away from murder and towards a lesser offense," Bederow told FoxNews.com. "Such a bold defense strategy suggests they are rolling the dice with an 'its not me' or 'this was an accident' defense.

The murder charge alleges Garnett was killed "under circumstances evincing a depraved indifference to human life" rather than with intent. It carries the same maximum sentence as intentional murder, however -- 25 years to life. The manslaughter count alleges Spears killed her son "while intending to cause serious physical injury."

FoxNews.com's Cristina Corbin and The Associated Press contributed to this report.