Usually, when a tourist is a victim of a violent crime, it’s reported by local news, so this would be a nice parameter to identify a threatening destination for foreigners.

However, even if someone is not murdered during his/her trip to somewhere, feeling unsafe, being victim of petty crimes or scams aren’t good travel impressions.

Actually, I think more travelers are killed in road accidents than by the hands of murderers…

The media is also a terrible barometer for determining how safe an area is.
I lived in the Washington, D.C. area during the sniper shootings. During the few weeks that the snipers terrorized the city and suburbs and killed several people, even more people died as a result of “routine drug violence” in the city. The only difference was that the drug killings never made the news. (Except for a few months later when a report came out showing how biased the media’s reporting is about murder).

There’s another problem. It’s often the case that the most ‘dangerous’ countries are underdeveloped ones, with very poor quality law enforcement. Many crimes, including theft and violence, go unreported. I personally know many victims of crime here in Buenos Aires (including me, several times) who never even considered reporting their case to the police.

If I wanted to scare myself, I’d look at a country’s road accident statistics.