What you would be looking for here is a direct correlation between the amount of violent video game content an individual has absorbed and a willingness, or lack of inhibition, to INITIATE violent behavior with others. In other words, prove conclusively, with no attributable X-factors, that playing a game with violent content made this person get violent. Not more likely to be violent (that's not a direct correlation), GET VIOLENT.
Put simply, you won't find one. I have NEVER, since I was aware of what a scientifically accurate study was, heard of one that demonstrated this.
You could make an argument in favor of desensitization, wherein violent or disturbing content lessens the averse reaction of a player to that content in future exposures, and you would be right; Dead Space isn't as scary the second time around (if it was scary at all for you, that is...modern Survival Horrors are like that). You could also make an argument in favor of the likelihood of violence, since there is an obvious psychological lack of inhibition, and therefore reduced chance of avoidance, against actions whose consequences the subject has been desensetized to. But that's been done, and it doesn't prove anything concrete.
For those of you who can't or don't want to decode that word pasta, there are studies out there that indicate that violent game content makes players less sensitive (read: less likely to be disturbed by) to violence. This is provable. It applies to ALL forms of media. There are NOT, however, studies that indicate that violent game content makes players violent themselves. The overwhelming majority of misunderstandings regarding this debate involve confusing those two.
If I were writing this report, I would dedicate a large portion of the paper to dealing with that problem. Identify both phenomena and draw a clear distinction. Ask me to clarify if you wish.
EDIT: Almost forgot, Moviebob covered this too. Link!
http://www.youtube.com/watch?v=hoht0Xy5nQs