The mammoth trial is being held in a congress centre in Siegen, in the state of North Rhine-Westphalia, near the refugee centre in the town of Burbach that was rocked by the abuse scandal four years ago.
The accused, among them centre managers, social workers and private security guards, face charges including false imprisonment, assault and theft.
Staff allegedly beat, tormented and humiliated asylum seekers or locked them up for days at a time in the facility that housed some 700 people seeking safe haven in Germany.
Police launched an investigation after journalists handed them cellphone video footage of security guards forcing an elderly man to lie on a vomit-covered mattress and threatening to beat him.
Other disturbing images that were released and sparked public outrage in September 2014 showed a guard pinning a handcuffed Algerian man to the floor with his boot on the man's neck.
“These are images of the kind we've seen from Guantanamo Bay,” Frank Richter, police chief of the nearby city of Hagen, said at the time, referring to the US military detention facility in Cuba.
Chancellor Angela Merkel's spokesman condemned the “repulsive acts” that had taken place at the centre located about 100 kilometres southeast of Cologne.
Refugee rights group Pro Asyl said the brutal attacks were signs of “appalling racism” of unqualified private security guards who were being hired amid a strong migrant and refugee influx.
Germany was already the top EU destination for asylum seekers from war-torn Syria, Iraq and other countries at the time, a year before arrivals skyrocketed to many thousands a day in mid-2015.