The Medico-Legal Expert Kari Omstad
Conspiracy theorists like to refer to the medico-legal expert Kari Omstad who performed the autopsy on Palme. She meant it was a sign of professionalism to only to fire one shot towards the body and not to the head: 
“To fire against the head is difficult if you want to be sure to hit. For once the head moves quite a bit and further more there is a big chance of surviving if you get hit in the head (sic!). You have to be a very good shot to avoid the risk that the victim will survive. It is very risky to shoot people in the head.”
Yes, for the victim who is hit from a very short distance! With a bullet of almost 9 mm the victim will face early retirement at best. He won’t remain Prime Minister. There is actually a reason why soldiers wear helmets. Christer Andersson was known as a good marksman.
Not all doctors share the views of Kari Omstad cf. the resistance fighter Kristian Hansen who during the German occupation executed several Gestapo-snitches in the town called Odense, Denmark: 
“The doctors had told us that we had to shot them behind the ears if they tried to get up. One time we blew off the nose of member of SS who was called Flash Gordon [= Jens Lyn in Danish]. After that the doctors told us that they didn’t like to help these crooks so we had to kill them properly. The head was the safest place.”
In the resistance movement BOPA they had no problems shooting snitches and other traitors in the head cf. the rapport that the leader of BOPA Eigil Larsen received from two saboteurs in October 1943: 
“We met two Schalburg officers at Kongens Nytorv [= in the city centre of Copenhagen]. They came walking with a couple of women. (…) When we reach the street of Bredgade we decided to shoot them down. We (…) reached them by Kongens Have [= Kings Garden] where we both pulled our guns and shot them both in their neck. They fell on the ground without a sound. The women that were with them didn’t even make a sound as we disappeared.”
 Cf. the classified part of the report of the Marjasin-Commission interview with Kari Omstad.
 Cf. Peter Øvig Knudsen : Efter drabbet p. 330
Cf. Morten Møller: Hvem er Nielsen? En fortælling om kommunisten og modstandslederen Børge Houmann, Gyldendal, 2012.