Are you saying batman isn't real?
We have plenty of Dojo Winter '94 in stock.
now see, Vash, you'll have us all believe in batman..
Honestly, there are several death strikes. The human body has it's vulnerabilities. As for just touching someone, you'd have to touch them pretty hard. If you had good short power, it might appear like a touch from the outside, but it'd still have to be quite firm.
Take your sternum strike for example. There's a small bony piece that sticks out of the bottom of the sternum called the xiphoid process. It's about the size of a fingerbone. If you can hit it just right, it'll snap off and sink into your liver. In days of old, that would probably kill you a few days later. So imagine a master who could deliver a subtle, yet powerful blow to the xiphoid process. His victim would go into shock, then probably die a few days later, akin to the myths of 'death touches'.
As for a touch that just kills someone like a pressing a button, I'd rather find the sexual pleasure button. That knowledge has more possibilities for improving my quality of life. ;)