Killer Knifeman or Innocent Defender?

A 52 year old VP of a Medical Center faces 95 years in prison for fatally stabbing a doctor's husband. He insists he was trapped, by a man intent on harming him, and forced to defend himself. But the Prosecution argues CCTV proves he's the aggressor and should be found guilty of manslaughter. Is he a killer knifeman or is he an innocent defender?