Matthew McMahon, 51, of Bel Air, was arrested Tuesday and charged with 10 counts of child pornography possession, according to Maryland State Police.

McMahon was a prominent figure in the trial of the killer of Rachel Morin, a 37-year-old Bel Air mother of five who was murdered on the Ma and Pa Heritage Trail in 2023. McMahon is the father of Morin’s eldest daughter and was a vocal advocate for Morin’s children during and after the trial.

He was the face of a lawsuit launched by Morin’s children against Morin’s mother, Patricia Morin, over money raised for the children through fundraisers after Morin’s death. The lawsuit ultimately reached an undisclosed settlement in September.

Police said McMahon was identified as having a connection to child pornography in September, when a trooper assigned to the Harford County Child Advocacy Center launched an investigation. Police served a search warrant on McMahon’s Bel Air home Tuesday, and said he was arrested on scene without incident.

According to charging documents, police recovered numerous videos and photos from a computer in McMahon’s room showing girls who were “undeveloped and flat-chested” engaging in sexual acts with adult men, posing for images fully nude and more. The documents said the children in the photos and videos were believed to be as young as 5 years old.

Police said McMahon is being held without bail in the Harford County Detention Center.

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