The US lawyer they hired was Miami's own Jack Thompson, of Stopkill.com. Thompson is the man behind every major US lawsuit concerning violence and video games and has made his services available for parents who believe their kids are addicted to video games.
What happened was a tragedy, and, in all honesty, "Manhunt" is an icky game, but nothing will be resolved by these lawsuits. The obsession with "Manhunt" should have been an indicator of something being wrong with the 17 year old. A healthy person doesn't find a game, and then start killing...and any good lawyer knows that.