From 2005 through 2008, 23 states across the nation have enacted laws generally referred to as "castle doctrine" laws or "stand your ground" laws. A castle doctrine law gives a homeowner the legal right to use force (even deadly force) to defend himself or herself and the family against an intruder. No study, however, has been conducted to evaluate its deterrent effects. The State of Texas enacted its castle doctrine law on September 1, 2007, and the subsequent Joe Horn shooting incident in Houston in November, 2007, served to publicize the Texas law to a great extent. The purpose of this study is to evaluate the deterrent effect of the Texas castle doctrine law and the subsequent Horn shooting on burglary in the two largest cities in Texas, Houston and Dallas. Daily data of residential and business burglary, over the period from January 1, 2007, to August 31, 2008, were obtained from the Houston Police Department and the Dallas Police Department. Interrupted time-series designs were employed in the study to analyze the intervention effects. The findings reported suggest a place-conditioned deterrent effect of the law and the Horn shooting; both residential and business burglaries were reduced significantly after the shooting incident in Houston, but not in Dallas.