Studies show that children who experience trauma are more likely later in life to suffer from asthma, depression, unemployment and to use drugs. The more trauma a child faces, the higher these odds. Children perform less well on standardized tests right after violent crimes have occurred in their neighborhood — even if they didn’t personally witness the violence.

The typical measures of trauma — “adverse childhood experiences” that include growing up in a household with physical or substance abuse — don’t gauge anything quite like witnessing lethal violence. That distress alters the picture of the population the Boston Reentry Study followed: These adults in the criminal justice system were once children exposed to awful things.

What, then, is to be done with the knowledge that four in ten prisoners typical to the Massachusetts state prison system saw someone killed as a child?