A federal judge in Florida has ordered a psychiatric evaluation of Thomas Markle, the father of Prince Harry’s wife, Meghan, to determine whether he is mentally competent to answer the charges brought against him concerning child sexual abuse.

In a two-page ruling issued on Friday, Judge Lindsay Griffin in Tampa, Florida, said that the 82-year-old father-in-law of Prince Harry’s initial court appearance — during which he said that he “doesn’t remember” — raised questions as to whether he is fit to stand trial.

Thomas Markle was arrested on Friday and faces one federal charge of possessing child sexual abuse material. The charge relates, among other things, to two obscene photographs in which he is pictured with a naked underage girl, as well as other images in which he appears alongside naked or partially clothed children.

One of the photographs depicts a naked girl in a room that appears to belong to a motel chain in the Philippines, a country where Markle lived for a period in the past.

According to an FBI affidavit filed in court as part of the criminal case against Markle, federal agents seized the material in question — part of a collection that included slides, film negatives and books — from storage units rented by Markle in Los Angeles since 2008.

Commenting on the case on Friday, FBI Director Kash Patel said that Markle had “targeted innocent children and sought to steal their innocence through his criminal acts”.

In recent times, Markle had been living in Lakeland, Florida, where, according to the Daily Mail newspaper, he had been staying in a care home.

No plea was entered during Friday’s hearing, while the judge allowed Markle, who had been held in custody, to be released on his own recognisance, on the condition that he be placed under house arrest and monitored electronically.

Following the hearing, Judge Griffin said in her ruling that she had found “reasonable cause to believe” that Markle may be “suffering from a mental disease or defect rendering him mentally incompetent to the extent that he is unable to understand the nature and consequences of the proceedings against him or to assist properly in his defence”.

Griffin said she based her conclusions on unspecified information regarding his health, his “advanced age” and his “memory lapses”.

The judge also appointed forensic psychiatrist Amy Gerodimou to conduct an independent psychiatric examination of Markle, diagnose his condition and determine whether he is mentally competent to stand trial.

Griffin set 20 November as the deadline for Gerodimou to submit her report to the court.