I don't know what it has been recently, but it used to run about one tourist a month killed. New Orleans has always been high on the per-capita murder rates, mostly friends and family type murders like any other urban area.
The crime doesn't really surprise me; the lack of response to it does. There was a guy on tv a minute ago calling from the Convention Center begging that the National Guard NOT be sent in.
Their whole infrastructure is down, no phones (cell or land lines), no electricity, most police cars under water, etc. They are running from place to place as they hear of problems.
I read in an article that the crime rate in NO is 10 TIMES the national average. That will explain a lot of what is going on. For a city that lives off tourism they have certainly shot themselves in the foot. No pun intended.