The mother said the Trazadone and her other prescriptions sedated her so heavily that Richins was entrusted with care of K.S. and his own infant daughter during the night, police wrote.
During the investigation, Richins "spontaneously" told police, "I only gave her 1.75 ml of Tylenol about 11:30," according to the charges. He also told detectives, without prompting, that he would never crush another drug to put in the Tylenol syringe, police wrote. He said he would never give Trazodone to a baby because "that would kill a baby."
Investigators found a half a Trazodone pill on top of the refrigerator, police wrote.
Richins was charged with first-degree felony child abuse homicide.
Richins who had not been arrested for the homicide as of Wednesday night was due in court next month in connection with the February burglary of a Sandy jewelry store.
According to charges filed in 3rd District Court, officers responding to an alarm at Sierra West Jewelry, 60 E. 10600 South, spotted Richins inside trying to break glass doors with a fire extinguisher.
There was also damage to display cases, ceiling tiles, heating ducts an wiring, totalling nearly $7,000, according to charges.
In Richins' pockets and a backpack, police found burglary tools and nearly $22,000 in stolen jewelry, according to charges.
Richins later admitted using a screw driver to pry open the back door, according to charges. He then crawled through the ceiling to get into the jewelry store, where he heard the alarm sound and began grabbing watches and jewelry to re-sell, according to charges.
When he tried to leave, he found he was locked in and tried to smash the glass door to get out, charges state.
He was charged with second-degree felony counts of theft and criminal mischief, third-degree felony burglary, and misdemeanor unlawful possession of burglary tools.
Richins has prior convictions from a 2008 case for assault on a police officer, assault on a health care worker, interfering with an arrest and intoxication, for which he was fined $4,500 and placed on probation for 24 months.