I’m sure we could all name few common characteristics of serial killers.

Narcissistic tendencies, antisocial behavior, and torturing animals as children all come to mind, but are you aware of the lesser-known traits that many murderers share?

If you aren’t, there’s no need to worry about missing out on important information, because here are a few more warning signs to watch for if you suspect that somebody might be a serial killer.

1. More than 60 percent of serial killers wet their beds past the age of 12, and criminologists consider this to be a major warning sign that children may grow up to become murderers.

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2. Murderers without any social structure in their lives likely can’t have normal sexual relationships and prefer auto-erotic activities.

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Some even become obsessed with masturbation, like Soviet serial killer Andrei Chikatilo, who had scars on his genitals because of how aggressive he was with himself.

3. Many serial killers often had some type of head injury when they were children that damaged their frontal lobe, which controls judgment, self-control, and social relations.

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4. It isn’t uncommon for mothers of serial killers to have abused alcohol or other substances while they were pregnant with them.

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5. Murderers and violent offenders tend to have higher levels of toxic metals in their systems like lead, cadmium, and manganese, which lowers serotonin and dopamine levels and causes aggressive behavior.

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For example, cadmium and lead were both found in mass-murderer James Huberty‘s body during his autopsy.

6. Most killers choose victims that share their race.

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7. We tend to assume that all serial killers are extraordinarily smart, but that isn’t always the case. In this study of over 200 serial killers, the average calculated from their combined IQ numbers was normal.

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8. Serial killers are fascinated by authority figures — so much, in fact, that many try to get military or police officer jobs.

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John Wayne Gacy and Ted Bundy both pretended to be policemen to get to their victims more easily.

9. A number of these people have tried committing suicide on more than one occasion — Charles Cullen attempted to end his life 20 times.

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Of course, these characteristics don’t apply to all killers, and having a few doesn’t exactly make you one of them. But they sure are creepy to think about, right?