Arapahoe County prosecutors say Collins and her boyfriend, Tyler Newton, had a bad habit of co-sleeping with their infants while using drugs and alcohol.
While the autopsy report lists the cause of death as "undetermined causes," the Arapahoe County Coroner's Office and Aurora Police Department detectives believe the child likely suffocated to death.
"Engaging in that conduct while perhaps under the influence of substances, that's always a bad decision for parents," Arapahoe County Deputy District Attorney Chris Gallo said.
Gallo said what made the 2016 death especially tragic is the couple had been warned by police and doctors not to sleep with their infants after the 2014 death of their first son.
Prosecutors have charged Collins and Newton each with two counts of misdemeanor child abuse, but the parents are being tried separately and so are the counts.
Friday's guilty verdict for Collins was for the 2016 death. She still faces trial in May for the 2014 death.
The jury was allowed to know about the 2014 co-sleeping death, but the jury that hears the 2014 case won't be allowed to know about the 2016 death it hadn't happened yet at the time of the alleged crime.
Newton goes on trial later this month for the death of his second son in 2016.