I picture Mark McGwire sitting alone in the dark somewhere, too ashamed to defend himself and too guilty to explain the reasons why.

Maybe I’m wrong. Maybe he’s on a golf course or picnicking with his family, no worries and no stress. But I picture him alone, and I cannot believe he is carefree right now.

I imagine McGwire following Barry Bonds’ trials and denials, watching Floyd Landis’ frantic foolishness and grimacing as he contemplates the sealing of his steroid-tainted doom.

I picture McGwire, several months short of his initial appearance on a Hall of Fame ballot, realizing that he is trapped and that his baseball life – once destined for easy immortality – is basically over now.

He had to know he had one final chance for a touch of redemption: Embrace George Mitchell’s investigation of performance-enhancing drugs in baseball, tell everything, do as much good as humanly possible.

McGwire intimated as much at that woeful appearance before the House subcommittee more than a year ago, when he refused to “talk about the past” but championed the cause of ridding sports of steroid use. That’s what he said. That is not the reality now.

According to a recent New York Daily News report, McGwire has declined to cooperate with Mitchell’s investigation, which has no subpoena power.

Nobody has refuted the report. Nobody from the McGwire camp has stepped up to bellow about the honesty of his performances as an Oakland Athletics and St. Louis Cardinals slugger.

Nobody is left to do it, except McGwire himself. And he won’t. Can’t.

Even before the Mitchell investigation began, I believed that McGwire’s Hall of Fame status, despite his 583 career home runs (seventh all-time), wasn’t certain.

I’ve run through the numbers one more time: His homer rate, while always high, skyrocketed in his mid-30s, exactly when he suddenly escaped the injury woes of his early career.

At the tail end of his Oakland career and throughout his St. Louis run, McGwire added a huge amount of muscle. Even with that extra mass, his previously fragile body did not tear or fray for most of five years. Weird how that happened, all of a sudden.

Jose Canseco dates McGwire’s steroid use to the late-1980s, but I trace his probable effective use to the mid-1990s.

That’s when McGwire transformed his career from very good (329 homers in 11 seasons through 1996) to Cooperstown-level (254 homers in his final five seasons).

Without that wild surge of power, which included the 70-homer festival in 1998, where is McGwire?

Factoring in normal declines because of age and his previous production, he hit about 125 more homers than could’ve been projected in his final five years. That knocks him down to 458 career homers, in the same non-Cooperstown ballpark as Dave Kingman (442) and Andre Dawson (438) and behind Fred McGriff (493).

By not participating in the Mitchell investigation, he is kissing off Cooperstown forever. It’s an admission that he has no excuse, no possible avenue for pardon or forgiveness.

McGwire, as a living, breathing sports entity, is done. He will never get into Cooperstown. He is just one of us now, a mortal, and he is probably alone.