Texas A & M University researchers say controversial "stand your ground" laws have increased the number of murder and manslaughter cases – rather than serve as a deterrent to crime, the Houston Chronicle reports. A study looked at 23 states that have passed "castle doctrine laws." Many critics say such self-defense statutes encourage vigilantism and escalate violence. At the center of that debate is the case of Trayvon Martin, the unarmed teenager fatally shot in February by neighborhood watch volunteer George Zimmerman.
Texas A&M 's Mark Hoekstra and Cheng Cheng analyzed crime data from 2000 to 2009, finding that murder and manslaughter cases increased between 7 to 9 percent in states with castle doctrine laws. The homicide rates in states that had not adopted castle doctrine laws remained steady, the study found. The study concludes that the laws "do not appear to offer any hidden spillover benefit to society at large." Hoekstra said homicides may have increased because more citizens used deadly force in a self-defense situations, instead of being required by law to retreat or use non-lethal force during an assault or other threatening circumstance. Another explanation could be that the number of homicides increased because force was used in situations that otherwise would not have been violent.