He has won a catalogue of Scottish and British titles in fencing, table tennis, basketball, and curling - a sporting career few could even dream of, yet his future looked very different the day in 1967 when he lay on his back on a mat in the spinal unit at Musselburgh's Edenhall Hospital, and realised he could not move.
Named last week in the Great Britain curling team for his third successive Paralympics and his fifth in all at 63, Killin is remarkable by any sporting standards.
It's 43 years since the Edinburgh man's first sporting success: two fencing bronze medals at the paraplegic Commonwealth Games in Edinburgh. And there were two team silvers at the 1980 Paralympics (Arnhem), and two team bronzes at the 1984 edition (Los Angeles).
"After that I got married, had a family and stopped fencing internationally," he said. "But I still competed in the British league at wheelchair basketball, and table tennis at world and British level."
For two decades he concentrated on these, representing Scotland and Britain in both. He won 11 Scottish Disability Sport table tennis titles - "they gave me the trophy to keep," he says. He was good enough to play mainstream table tennis in the Edinburgh and Lothians League for many years.
That all stopped, however, after a chance encounter with Michael McReadie, a former GB basketball team mate, while shopping with his wife at Braehead.
McCreadie was on his way to curling at the neighbouring ice rink. "I had never curled at all, but he suggested I try it. That was in 2004, the following year I was in the team that won the world title."
He has played in every world and Paralympic championships since, taking silver in the former in 2011 and Paralympic silver in 2006. He was among the 20 sportsmen and women in the inaugural intake to the Scottish Disability Sport Hall of Fame.
It is a reality he could never have begun to grasp in 1967. "I had a car accident - a spinal injury. I am an incomplete paraplegic. I have minimal movement in my lower body. I was in Edinburgh Royal Infirmary for three months and then in the spinal unit at Edenhall.
"The time you realise it is when they take you out of your chair, and put you on a mat on the floor. They lay you on your back, and you just can't move. 'How the hell do I get up from here?' I thought. That's when you realise the extent of your disability. You're trying to get on your knees and stand up, and you just can't do it. It really hits you like a ton of bricks."
The sporting world has changed dramatically since his first major event, in 1970. "It was called the Paraplegic Commonwealth Games then. It was a few weeks after the Commonwealth Games, and at the same venues, but we stayed at RAF Turnhouse - not the university halls at the Pollok, because of the stairs."
Killin's nomination for Sochi next year makes him the only ever-present in the curling squad since the sport was introduced to the Paralympics for Turin in 2006, when the team won silver. Skip Aileen Neilson, from Strathaven, is the only other survivor from Vancouver in 2010. Gregor Ewan (Elgin) and Bob McPherson (Bellshill) complete the team. A reserve, or alternate will be named in December.
The irony of going to Russia next year is not lost on Killin. He should have been at the 1980 Paralympics, scheduled for Moscow, but the Soviets did not acknowledge the existence of disability - perversely attempting to make it a virtue by stating that everyone was born equal, despite having no platform for disabled sportsmen. Today, refusal to host the Paralympics would debar any Olympic host.
The event was reorganised for Arnhem, where Killin won his two team fencing medals. Now, 33 years on, he finally gets his Paralympic chance in Russia. "You could look on this as a massive step forward in the disabled world," he said, "but I don't get into the politics of it."
Killin was at the Paralympic World Championships last year. "We were fourth equal, but sixth after the play-offs. It was disappointing, but gave us a flavour of the Sochi venue.
"I stopped playing all the other sports when I started curling seriously. Nowadays, international sport is so professional you have to do one, and stick to it. When I started, you could jump about and do two or three. Now you have to dedicate yourself to one.
"And with lottery funding, and the Scottish Institute of Sport, I don't think they'd let you jump about.
"It's so demanding - we train five or six days a week on the ice and in the gym - harder now than I ever did in my life. We have a really good squad, technically probably the most powerful team in the world. We have a new Canadian coach, Tony Zummack, whose vision and concept of the game is way ahead of his time.
"At the last worlds, I was top of the percentages in my position for the whole tournament. I am playing better now than ever. I have changed my delivery position, got a handle on my chair, and changed my whole style of play.
"The handle stabilises my delivery. I have a smooth fall forward. It's easier demonstrated than described, but it has helped turn my game around. I thought I was good, but I realise now that I wasn't nearly as good as I thought I was - but I am now, if that makes sense. It's all down to Tony.
"We have trained all summer for the past two years, when we used to take time off. We are constantly training, summer and winter. We are lucky to get ice at The Peak, in Stirling. The only time we had off this year was in July. Otherwise it's been solid for the past two years, and we are in better shape than I can ever remember, technically, and teamwise.
"I believe we have a real chance in Sochi. First, you want to make the semi-finals, and after that there are only the podium places left. I don't see any reason why we can't do that. Our technical ability, understanding and reading of the game, has improved so much recently, it's unbelievable.
"Tony is on the ice with us. We train 7-8 hours a day. We have a camp this week: Braehead on Monday and Tuesday and Geenacres from Wednesday to Saturday. That's the kind of work we're putting in, and I don't think any other country is doing this.
"The lottery and the institute backing has given all this time to train which we have never had before. We're better prepared than I can ever remember - a full-time physiotherapist, sports psychologist, nutritionist. It's all constantly on tap, when we need it. We have had it in bits and bobs before, but never this kind of package.
"We have a few competitions coming up: Denmark in a fortnight, Vancouver in October; then in November we are back to Canada -Ottawa; then Utica in the US. So we will have played a few of our rivals before Sochi. It's a great chance to stamp our authority, hopefully.
"There is a lot of pressure to perform on the run-in, a chance to get an edge over them, and that's what we are looking for. If we play consistently, we can probably get medals."
Gold would give him a Paralympic medal of each colour, and put him upsides with his wife, Maggie. "We met when we were both fencing for Britain, but she has won two golds.
"I'm enjoying playing now more than at any time in my life. I'm in a really happy place when I am curling, but I very much doubt if I will do another Paralympics.
"I'd love to go into the coaching side after this. I would like to put something back in, helping wheelchair athletes."