Is it permissible for a lawyer to defend a perpetrator of a crime by requesting a reduction of their sentence?

It is not permissible to defend perpetrators of crimes, for Allah Almighty says: (And do not argue on behalf of those who deceive themselves. Indeed, Allah does not love one who is a habitually treacherous sinner.) [An-Nisa: 107]. However, there is no objection to requesting a reduction of punishment or interceding on behalf of those who commit sins, especially if the perpetrator is not known for such transgressions. Ibn Abd al-Barr said: "I know of no disagreement that intercession for those who have committed sins is a good and beautiful act, as long as it has not reached the ruler." The restriction on the permissibility of intercession before it reaches the ruler applies specifically to crimes that carry a fixed legal punishment (حد). As for crimes that do not carry a fixed legal punishment, there is no objection to interceding for them, even if it has reached the ruler.