If waiting periods affect anything (and I'm not saying they do, we don't have one so how would I compare?), I'd venture to say it's suicides. I haven't kept stats because I don't care that much, but the only murder I can think of with a new gun was a voluntary murder/suicide (the "murdered" person also left a suicide note, the murdered person was terminally ill and the couple decided to punch out together). I can think of several suicides with newly purchased guns, and a hand full with rental guns, ie go to the range and pop yourself. Every once in while we'll have some one bring their own shell, ask to see a shotgun at a department store or gun shop, and then quickly load it and pop themselves. One guy actually asked the clerk "Do you have a shotgun that holds this shell?" first. Eh, sorry, wandering afield. Point is outside of child abuse murders, it rarely seems to be heat of passion. Suicides seem to be more spur of the moment more often.