For the past 47 years, Jeffrey MacDonald’s account of what happened the night his entire family was murdered has stayed the same.

So has the case against him, built largely on blood-type testing — he, his wife and two children all had different blood types — that seems archaic by today’s standards.

But since his 1979 conviction, MacDonald has painstakingly gathered a body of evidence — some of which was suppressed by prosecutors — via Freedom of Information Act requests that he believes prove him right.

“I am innocent,” he says in an exclusive jailhouse interview in this week’s issue of People magazine.