Johannesburg - Justice Minister Michael Masutha's decision to suspend Paralympian Oscar Pistorius's release on parole this Friday is not unique, law expert Mannie Witz told News24."He has done it before with Clive Derby-Lewis and the Waterkloof Four," Witz said. "There has obviously been some form of pressure and a petition, which the minister would need to consider."Justice spokesperson Mthunzi Mhaga said earlier that Masutha had considered a petition to stop Pistorius's release and had referred the decision to the parole board for review.This implied that the earlier decision to release him on parole "has been suspended", said Mhaga.Witz said reaching a decision to release a prisoner on correctional supervision was not a simple task and involved multiple checks and balances.According to Witz, the Correctional Supervision and Parole Board (CSPB) had to, among other things:- Check if Pistorius was a danger to society;- Decide whether he would be self-sufficient outside of prison;- Monitor his behaviour while still in prison;- Check his previous residential and work record. Pistorius would also have been required to make a sworn affidavit showing remorse for the crime committed, said Witz. "You have a whole committee of different people to sign."Witz said the process was not quick either. "There must be something new, over and above what the department of correctional services has done."In June, the CSPB confirmed Pistorius would leave the Kgosi Mampuru II prison in Pretoria on August 21.On October 21 2014, Pistorius was sentenced to five years in prison for killing Reeva Steenkamp, and three years - suspended for five - for discharging a firearm in a restaurant.Wednesday would have been Steenkamp's 32nd birthday.