http://www.universalhub.com/crime/dorchester.html http://www.universalhub.com/crime/roxbury.html
(I have family in Roxbury, Dorchester and Mattapan)
Generally speaking, the areas around MIT and Harvard are relatively safe, although muggings and petty theft aren't unheard of. Things have been a lot better since they cleaned up Central Square in the 1990's.
Note that the following link only include incidents in which bullets actually hit people. http://www.bpdnews.com/wordpress/wp-content/uploads/Shooting...
Has it really gotten a lot safer. not counting this unique sort of incident?
This does not, of course, include justifiable homicides.
ETA: So as not to scare anyone remember that in major cities typically between 65% and 91% of murder victims are criminals, and most of the killings are gang related.