Should injustice be answered with justice or mercy?

Injustice can occur in many forms nowadays. It ranges from the extreme cases of victims of murder, assault and rape, to the cases of theft and biases. I assume those who go by law might chose to fix this by justice and those with faith and belief (in the good of people) might chose to deal with the problem with mercy. They say mercy is taking the "higher road"....but how many of us are actually capable of it? As much as I would like to think I am capable of mercy, when I feel like I am being treated unjustly, all I want to do and work towards, is getting my share of justice. I'm sure we all face unforgiving moments in life. Maybe such moments define us...as a person. When it comes down to it...when we are the ones to decide and face the consequences of that decision. What do we chose?