Christian B, as he is known under German privacy laws, reportedly needed hospital treatment following the altercation.
The suspect in the Madeleine McCann case has been injured after an argument in a court cell, according to a German newspaper report.
Christian B, as he is known under German privacy laws, was waiting for the start of a parole hearing in a bid for early release from a current drug-trafficking jail sentence
He suffered two broken ribs and needed hospital treatment, according to the national newspaper Bild.
His lawyer, Friedrich Fulscher, is said to have a filed a formal complaint against the suspect’s guards and an investigation was launched.
Mr Fulscher, who is thought to have witnessed the incident, refused to comment when contacted by Sky News.
Christian B, 43, had been driven to the hearing in Braunschweig’s High Court from his prison in Kiel two hours away in Northern Germany.
The German drifter is the prime suspect over the disappearance of British girl Madeleine McCann, who was nearly four when she vanished from a holiday apartment in a Portuguese holiday resort in 2007.