A mother was on the computer in the kitchen when a visitor found her 10-month-old son submerged in an overflowing tub with the water running, according to an arrest affidavit.The infant, Aldrich Leathers, was pronounced dead later that night, on Sept. 20, at a hospital. His mother, Muriel Keer, was formally charged with felony child abuse resulting in death on Tuesday, said Denver district attorney spokeswoman Lynn Kimbrough.The 39-year-old Keer remained in the Denver County Jail on $100,000 bond.7NEWS has reported that the infant spent the first months of his life in the care of Denver Department of Human Services after he was born to Keer while she was jailed for drug possession.After being released on bond last fall, Keer was jailed again for violating probation by failing two drugs tests for methamphetamine and opiates, court records show. This happened just days before Aldrich's birth on Nov. 27, 2010.Keer regained custody of her child in the spring and was on intensive supervised probation when the infant died, roughly four months in her custody.On the night of Sept. 20, Denver police were called to Keer's home at 2725 E. 33rd Ave. on a reported baby drowning in a bathtub.Zachery Hopkins told police he was visiting his boyfriend, who rented a basement room in Keer's house. The two men went outside to smoke cigarettes.Hopkins said he went inside to use the bathroom and saw Keer working on the computer in the kitchen, according to the arrest affidavit.In the bathroom, Hopkins said he found the baby boy lying face-up under the surface of the water with toys floating around him, the affidavit said.The faucet was still running into the brimming tub and water was flowing into an overflow drain, the affidavit said.Hopkins said he lifted the unconscious infant from the water and called 911, the affidavit said.Neighbors told 7NEWS they heard the mother screaming, "Not my baby!" as the limp child was carried to an ambulance.When a police detective told Keer she was under arrest, she asked for an attorney, the affidavit said. But as the detective was leaving the interview room, Keer said her baby had diaper rash and "there was no abuse," the affidavit said."The suspect is currently on probation for drug-related offenses," the affidavit said. "The suspect has a history concerning the victim with the Denver Department of Human Services."Keer pleaded guilty to felony methamphetamine possession in December and received a suspended four-year prison sentence and four years of intensive supervised probation, court records said.She entered a female offender drug treatment program, and her baby remained in the custody of the Human Services agency for about five months, 7NEWS learned from court records.Last spring, the baby was returned to his mother.For Aldrich's first month at home, an in-home monitoring service was checking up on Keer and her infant, 7NEWS learned. Denver Human Services deemed the transition a success and closed its case.After that, the only official watching Keer was her probation officer.