One day after surrendering and pleading not guilty to killing her son, Lacey Spears has been placed on suicide watch at the Westchester County Jail.

Prosecutors say medical tests, video evidence and Internet searches will prove that the Rockland native made her 5-year-old son so sick, it killed him.

Spears is being held without bail. Spears was charged with second-degree murder and first-degree manslaughter during her arraignment.

Investigators say Spears poisoned her son, Garnett, by putting sodium into the boy's feeding tube, which Spears claimed he needed due to a chronic gastrointestinal condition. They believe much of the poisoning happened at the Fellowship Retirement Community in Chestnut Ridge where Spears worked and lived.

Police also say their investigation uncovered computer records that showed Spears searched the Internet to research the type of effects salt would have on her son. Prosecutors say they have obtained what could be damaging video.

"As the defendant is taking her son into the bathroom, as you see in the video with that connector tube in her hand and that cup, that coincides with the EEG machine that goes from moderate to severe cerebral dysfunction and as that is going on, the sodium levels keep going up," says prosecutor Doreen Lloyd.

They also add that medical tests will show regular and irregular CT scans.

Lloyd told the court that Spears allegedly asked a friend to get rid of the feeding tube she was using for her son just after his death.

Spears' attorney says the young mother was doing the best she could to better the life of her son.

Prosecutors believe Spears may suffer from Munchausen by proxy, which is a disorder where a parent sickens a child to gain attention for themselves. So far no psychiatric testing of Spears has been ordered by the courts.

Spears is due back in court July 2.