Sure, but if I gave someone a thump on the nose I would use my strongest hand.

And John isn't just trained in self defence.
He's a trained killer, a bit like his wife.

John is indeed left-handed but he isn't very left-handed. He seems to do several everyday things with either hand.  There was a lot of discussion about this post-Season 1 when people noticed that sometimes he holds a fork in his left hand and sometimes in his right, or he'll pick things up (e.g. the little pot in the Lucky Cat Emporium) with his right hand.  I'm assuming that this is a Martin thing rather than something scripted or directed.  I don't think Martin is actually ambidextrous but it seems that he's comfortable using either hand for some simple tasks. 

It was noted that John shoots with his right hand probably because it's easier to hold and fire a pistol with the right hand, and that many left-handed people undergoing training to fire guns give up trying to use their left hand and make the adjustment.  It's only people who are very left-handed and simply can't use their right hand easily who have no choice but to use their left hand and have to cope with the problems of the fact that guns are designed for right-handed people. 

Whether Martin decided to hold the pistol in his right hand or was asked/advised to by the armourer is something I don't think has ever been answered, but seeing as Martin seems to have little difficulty using his right hand for most tasks, I imagine that he automatically used his right.

As far as punching Sherlock with his right hand is concerned: it's possible that John can punch better and harder with his left hand than with his right, but when Sherlock says, "Punch me in the face," he gestures to his left cheek.  In order to hit that side of Sherlock's face, John would find it easier to use his right hand and so, being the good little soldier who automatically obeys orders, he uses his right to aim for the cheek which his commanding officer(!) gestured to.  I also think that he knows that if he punches him with his stronger/dominant hand he'll do him far more damage, so instinctively switches to his weaker hand, which is why he also uses his right hand when he has a second go at him a few seconds later.

While we're on the subject, I'm sure this has been mentioned elsewhere but I loved the observation from sharp-eyed viewers that in TAB, Watson takes notes with his right hand.  Many left-handed Victorian children were forced to write with their right hand, so whoever remembered this and advised Martin to hold the pen in his right hand deserves a million kudos points.

Last edited by Ariane DeVere (May 10, 2016 8:47 am)

Thats right, I can remember that there was a time that left handed children were forced to use the right hand.
I looked after Johns background story again and found out, that he actually had a gunshout wound on his left shoulder, so that could be also a reason why he used his right fist.

I apologise in advance...
I am giggling very childishly at the thought of John doing things with his hands.