The police are hoping that finding out the "who" might lead to the answers of some of the "whys".
Why did the man travel all the way to the moorland track where he was found? Why there? Why poison? Why strychnine?
Some count the area where the body was discovered as being part of Saddleworth Moor.
It is very popular, especially on a bright summer's day. Not only walkers but cyclists and climbers come here, and sailors on Dovestone Reservoir.
But it is also a place associated with a number of deaths over the years.
Peak District National Park Ranger Andy Valentine was brought up close by and now often takes his 4×4 past the spot where the man walked on that day back in December.
Driving along the bumpy track, he notes that the area is very close to where Ian Brady and Myra Hindley buried their child victims in the mid-1960s.
"If those trees weren't there, you would be able to see the hillside where the first of the bodies were found."
Further up, the car passes some ragged rocks jutting skyward. It is known as Indian's Head.
"There are four aircraft wrecks within less than a mile of this spot," Valentine continues.
He points out where a British European Airways DC-3 came down in 1949.
One theory, still not completely ruled out, is that the man's death was somehow connected with that.
Twenty-four people died. Eight survived. For a while, there was speculation that the man could have been one of them, coming back to the area where the crash happened. But the one remaining survivor is alive and well.
Valentine looks out towards a place called Wilderness Gully.
"Just across the valley, probably 200 yards away, is the site of an avalanche, in 1963, which claimed the lives of two of England's best mountaineers at the time."
Going back a lot further, to the 1800s, "a landlord and his son were murdered by unknown assailants" and, a few years later, there was the accidental shooting of an MP.
"This area is no stranger to tragedy," observes Valentine.
For whatever reason, the man travelled nearly 200 miles across England to be there. To go to that place to die.
"Why has he undertaken that journey?" Coleman asks. "Why did he travel on that day? What's the connection to the area?"