PHILADELPHIA (CBS) – A daring escape helped lead to an historic sex trafficking conviction in Philadelphia. A jury convicted 50-year-old Richard Collins, of Kensington, on Aug. 9 following an investigation led by the Philadelphia Police Department’s Special Victims Unit and the cooperation of five female victims.

Collins was convicted on four counts of trafficking individuals, three counts of involuntary servitude, one count of rape, one count of aggravated assault, and one count of strangulation. It’s the first-ever conviction involving trafficking of adults in the city.

One of the five victims was killed in a domestic violence incident, not related to this case, before the trial and three others testified on Friday.

“This is very difficult to prove,” SVU Lt. Harold Lloyd said. “They have to come to us and give us information and most of these people do not identify themselves as victims.”

The Philadelphia District Attorney’s Office says the investigation began on June 18, 2018, when one of the victims, who is now deceased, fled Collins’ house on the 800 block of Hilton Street in Kensington and contacted the SVU to report that three other women were being held inside the home.

The victim reportedly climbed over barbed wire fencing to get help after realizing what was going on inside the home.

A search warrant was executed within hours of the SVU call and the three victims were removed from the home. Investigators found there was also a fourth woman inside, she was also recovered.

The investigation found that Collins preyed on the victims’ opioid dependency and offered them shelter and access to drugs inside his home, then forced them to engage in commercial sex in the Kensington area.

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The victims ranged from age 20 to 28 and were subjected to physical and sexual assault.

Collins would punish the women by denying them opioids, which they were addicted to, causing them to become extremely ill.

“We had severe assaults that occurred as well, so there was a series of events that led to them being controlled based on the violence, the drug withholding, the actual basic needs of sleep, a place to live, of food and shelter. All those things, they were wholly dependent on this man,” Special Victims Unit Officer Ashley Capaldi said.

The case was prosecuted by the District Attorney Office’s Family Violence and Sexual Assault Unit.

“Trafficking cases involving adult victims are historically difficult to prove, in part because of a stigma associated with commercial sex work as well as harmful misconceptions about people who struggle with addiction,” District Attorney Larry Krasner said. “This conviction is the product of our collaborative effort with local and federal law enforcement and social service providers in communities hardest hit by the addiction crisis, the drug and human trafficking trades, and poverty. I am grateful to all of our Human Trafficking Task Force partners, and to the brave women who helped us remove a destructive individual from the Kensington community. May they know healing and peace in their lives moving forward.”

Collins is set to be sentenced in October. His victims are taking steps to recover from their addictions.

CBS3’s Matt Petrillo contributed to this report.