Finding hidden evidence of domestic violence

In the dark world of domestic violence, strangulation that stops short of death is often a sign of deadlier acts to come. Bruises from strangulation do not always show under white light. Now Tucson Police have a new type of light available to them that can make invisible bruises visible, and strong evidence.

Before Michelle Ohnesorgen Johnson was murdered, the man who killed her, then killed himself was still facing an earlier domestic violence case that charged him with strangling her.

Experts in domestic violence say victims who survive strangulation are seven times more likely to be murdered as domestic violence persists and gets worse.

But strangulation may not leave any marks that would help police build a case.

Now donations from the League of Women Voters and the Erik Hite Found