Biometric Signature- A Way To End Illegal Commerce?

It has been argued that biometric signature can be the way to end all sorts of illegal commerce, from prostitution to the sales of illegal guns, drugs, and so forth. Whereas cash will not leave any sort of trail, if all transactions in the future were electronic and had a step that required   biometric signature  identification or authentication, these scourges may be ended. However, this will only be possible in a cashless economy and will unlikely to be possible any time soon. However the idea of biometric signature making the world a better world in this way is a very interesting proposition however, that should bear much analysis.