The Weapon of Choice

The trouble with writing crime short stories is that although I can come up with endless characters and situations I have trouble coming up with weapons and a good description of the crime--forensics stuff. Usually I can write around it, but in a story I'm working on now, I need to choose a weapon for someone to use in a lab. At first, I thought of a dart gun. Makes sense they would have tranquuilizer guns around with lab animals. But it seems to make the whole scene humorous. So now I'm using a knife. Does any ordinary Joe know knife skills well enough to kill? A gun enters the scene later, so I can't use that. I guess I need to buy some books on weaponry and forensics. Or stick to off-scene murders. Or go back to tragic stories of Alzheimers's patients and lost loves.