Domestic homicides are some of the most depressingly common murders the cops see. Thirty percent of women who are murdered are killed by a partner. But there’s some red flags you can keep watch for.

The Chicago Tribune reports that Northwestern University researchers are profiling common traits of those most likely to kill the people closest to them after 1,500 hours of what must have been some seriously fucked-up conversations with 153 convicted murderers.

Here are the shared characteristics:

  • Severe mental illness
  • Cognitive impairment
  • A lack of prior felony convictions
  • Lower IQ scores

Also, just 14 percent of those committing domestic homicides used a gun, presumably because it tended to be a crime of passion done without premeditation. Somebody just snaps and there’s no time to load the pistol, they just go with whatever’s handy. In non-domestic homicides, 59 percent used a firearm.

Most of these traits seem obvious once you’ve got them statistically nailed down. Then again, maybe not obvious enough, as long as 1 in 4 women reports being a victim of domestic abuse. And that lack of prior felonies is a curious one. When some people finally snap, it appears, they do so in the worst of ways.