Sympathy was the exact reason Oscar Pistorius chose to remove his artificial legs and walk on his stumps. In order to gain special allowance in sentencing and prison, Pistorius did the last and most powerful gesture he could. The spectacle of him walking around on his stumps and weeping afterwards was geared to impact the emotions and sympathy of the court. The court has no choice but to consider Pistorius' disability.
The case of Oscar Pistorius is a very strange and disturbing one. The fact that a track star with artificial legs brutally shot and killed his girlfriend, whom he thought was an intruder, supposedly, is a very hard pill to swallow. Maybe the fact that he is disabled might incur sympathy from the courts.
Oscar Pistorius will not gain any sympathy after removing his artificial legs at his sentencing hearing. Many will see this a blatant attempt to influence the court. The public outcry has led to pressure to increase his sentence. Many do not believe his story and think he killed his girlfriend in cold blood.
I believe having Oscar Pistorius remove his artificial legs was more of a tactic than a strategic move. It was something the lawyers did to only add more shock value to the situation and the trial. I don't believe the stunt will garner him any more sympathy during his trial.