Based on training and experience, and also based on the information that I was given, you're not going to have fine ridge detail during a violent encounter. It would be different if this gun was like this and someone just came up, other than the officer, and touched it.
When we process that, yes, you can get fine ridge detail. So the decision was made between myself and the crimes against person detective, homicide detective, that it would be better to swab the weapon.
Now, if you are going to swab it, then you need to swab all the relevant areas that could be touched by someone other than Darren Wilson.