Question

At “show” trials during the Great Purge, suspects often

Answer 1

At “show” trials during the Great Purge, suspects often admitted to fault even when they were completely innocent, in the hopes of receiving a reduced sentence or avoiding the labor camps in the East. 

Answer 2

I believe the answer is: confessed to crimes they could not have possibly committed

The evidence that was presented based on 'examination' by government, and many confessed that those evidence were fabricated by the Secret Police. Many also give the testimony that the defendant were forced to confess to the crimes because they are put into extensive torture and intimidation.