I don't know for sure what happened in this particular case, but as a general rule, mistakes happen . . . and police and prosecutors ought not be punished for an honest mistake.
BUT! When a wrongful conviction comes about because of misconduct or malfeasance on the part of police or the prosecutor (such as with holding exculpatory evidence) then IMHO those responsible ought to go to prison for at least as long as the wrongfully convicted person did.