Juries may not buy the argument that the two shots are all part of a single event. Expecially if witnesses recall any hestitation between the two or if the physical eveidence sugguests that the BG was incapacitated when executed by the second.
For the past 5 years, I've been training at Front Sight in Nevada. I attend not less than two times per year and sometimes three. I've taken defensive handgun courses, practice rifle, and tactical shotgun courses among others.
In their defensive handgun course (basic handgun training), there are no situations when two controlled shots to the thoracic cavity are not always delivered. The standard training scenario is a controlled pair to the chest.....determine if the threat still exists, and if it does, then you just entered into a failure to stop situation. (body armor in use, amped up on drugs, etc.) Failure to stop is completed with a single head shot to the cranial ocular cavity (brain box). The skills test (end of course evaluation) is conducted in this fashion as is the 4 days of intensive training.
In practical rifle (typically shot with an AR-15), we practice controlled pairs to the thoracic cavity quite often when at 25 yards or less. However, during the skills test, only single shots are performed on target.
I just finished a 4 day advanced tactical shotgun course last week. During day #3, we spent the entire afternoon working through scenarios which included a car jacking, clearing a five room shoot house, a Hogan's Alley type situation, and Shotgun Alley (a steel target rich environment set in a canyon/wash in the desert). During the car jacking scenario, I was stopped by 4 bad guys. When deploying a handgun for this situation, the correct response was to put 1 shot into the thoracic cavity of each bad guy (closest to farthest) immediately followed with a second shot to each. Once the 8th shot was delivered, you then accessed the situation to see if any threat(s) remained....and dealt with it accordingly.
By the time I made it to the shoot house, I had already shot the car jacking and shotgun alley. The first three rooms I cleared resulted in double taps using my FNH SLP semi-auto. The instructor comments during the debrief? "Nice doubles on the first couple rooms. Great recoil control and 2nd shot follow up." The muscle memory from those thousands of controlled pair shots I've delivered at Front Sight and at my local range kicked in while in the shoot house.
It matters little to me if you agree or disagree with what I've written. I posted to this thread to show that "double taps"....I prefer the phrase
controlled pair....is an industry standard technique. Front Sight training well over 1000 students per week. For me, the split time for the 2nd shot of the controlled pair is around 180 milliseconds. A controlled pair is indeed one event on one target when I am shooting.