Yes, i feel that Justice and Mercy can co-exist. Justice means is the quality of being just and fair and displaying righteousness, equitableness, or moral rightness. To uphold justice, you need to be display righteousness and at the same time being equal to all.
Many people feel that justice is punishing people who commit crimes and violated the law. However this is wrong thinking. Justice should be about dishing out the punishment to the ones who commit the crime and not by their own revenge like how Shylock did in The Merchant of Venice. This shows that Shylock was keen on revenge more than upholding the justice.
What about mercy? Mercy is about being forgiving and is a divine virtue, only for the blessed and the kind. The often hard and cold aspect of justice is sometimes affected by mercy. Mercy is an act of forgiving and sympathy. Only cold and cruel people do not feel sympathy and thus, there are many cases where the guilty was released due to the showing of mercy from either the victim or the jury.
One case is about Ameneh Bahrami, an Iranian woman who was horribly disfigured in 2004 after acid was splashed on her face by Majid Movahedi, whose marriage proposal was rejected by Bahrami and in a fit of anger, disfigured Bahrami. The Iranian law states that since Ameneh Bahrami lost an eye, Movahedi's should also remove an eye, according to the law "Qesas", which is basically "an eye for an eye". However, Bahrami decided to be merciful and spared Movahedi of this horrible fate, with the main reason being that Bahrami could not bear to hurt another fellow human being.
This is a very good example of how Justice and Mercy co-exist. The justice is shown when the court summoned Movahedi to have his faced splashed by acid. Mercy is then shown from Bahrami when she decides to forgive Movahedi.
In conclusion, I feel that Justice and Mercy can co-exist. They rely on one another to have a fair judgement when punishing a criminal.