I don't think there were meters of blood. Blood smears. In a picture it might look like a lot of blood, but may just be smears. I believe that is what the ME was saying (tweets are not that great). If someone was bleeding from a cut or torn flesh (depending on whether it is a head injury) it could look like a lot of blood when it is a tablespoon of blood smeared across a surface. If there had been pools of blood, the ME would have stated as much and could tell if it was fatal. With three individuals, it would be harder unless pools of blood were discovered. She used a scientific term of bloodletting. That means someone bled. When I hear bloodletting, I think of someone draining blood, but technically, bloodletting could be a paper cut. The ME is just testifying to her experience. Others will have to testify to theirs.
"Police would not comment on the drag marks, which ran about eight metres from a side door to the driveway and appeared to be a dark liquid that was recently cleaned up."
http://www.calgarysun.com/2014/07/0...lgary-grandparents-and-young-boy-went-missing
The ME seems to be testifying about the opinion of others. She is unable to say whether the victims were alive or dead when they were removed from the Liknes home. This does not mean that they were alive at Airdrie, but the prosecutors are hoping that the jury is too stupid to see this - that they will assume the worst.