The Independent Police Complaints Commission (IPCC) is to manage an inquiry into the arrest of a young Asperger's syndrome sufferer.
The man, 18, was held on suspicion of causing criminal damage on 15 July and taken to Stourbridge police station.
He was released without charge wearing a white paper suit given to him by West Midlands Police, and arrested again the next day, still wearing the suit.
His mother complained about her son's treatment, sparking the inquiry.
The second arrest was made in Stourbridge town centre, the IPCC said.
The man, who cannot be named, was detained on suspicion of possession of an offensive weapon.
He was again taken to Stourbridge police station, from where he was transferred to hospital under the Mental Health Act.
The matter was referred to the IPCC after the mother's complaint and officers from the professional standards department of West Midlands Police are now carrying out the investigation under the direction of the IPCC.
John Crawley, IPCC commissioner for the West Midlands, said: "I will be looking at this case both as a specific incident to be investigated and to assess whether it raises any wider organisational learning issues for the force.
"I will be offering to meet with the family to hear their concerns and to explain our role in this investigation."