A 27-year-old woman was sentenced to 20 years to life in prison on Wednesday for using salt to poison her 5-year-old son to death.

Lacey Spears, of Scottsville, Kentucky, was found guilty on March 2 of second-degree murder in the 2014 death of her only child, Garnett-Paul Spears, at a suburban New York hospital.

Prosecutors sought the maximum sentenced of 25 years to life, but the defense fought for the minimum sentence, which was 15 to life.

On Wednesday, acting state Supreme Court Justice Robert Neary called the crime an "unfathomable in its cruelty" at the sentencing trial, according to CBS New York.

He added that Spears brought her so "five years of torment and pain." However, he decided not to impose maximum 25 years to life reasoning that "one does not have to be a psychiatrist to realize you suffer from Munchausen by proxy."

"By not imposing the maximum sentence, I'm combining punishment with something that you really did not exhibit towards your son, namely mercy," Neary said.

According to USA Today, Munchausen by proxy is a disorder that caused Spears to purposely and secretly harm her child so that she could enjoy the attention and sympathy she received.

During the trial, prosecutors argued that Spears presented herself as a devoted mother and mommy blogger on the Internet. However, in reality, "this mother was intentionally feeding her child salt at toxic levels," said prosecutor Doreen Lloyd at her arraignment, according to The Associated Press.

Prosecutors also stated that the single mother administered salt through a feeding tube into Garnett's stomach while he was at the Westchester Medical Center in White Plains, New York, reports Time. As a result, the boy's sodium levels became lethal, leading to a swollen brain, seizures and eventually death.

Spears chronicled her son's life, many hospital visits and sickness online. She also shared 28 posts documenting the last 11 days of his life.

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

"Garnett the great journeyed onward today at 10:20 a.m.," Spears wrote on the day her son died.