It is the longest-running criminal case in U.S. history, and one of the most horrifying murder cases of its time, with chilling echoes of the Manson Family’s “Helter Skelter” killings: Jeffrey MacDonald, a handsome, Ivy League–educated Green Beret Army doctor, accused of brutally stabbing and clubbing to death his pregnant wife and two young daughters in the middle of the night. MacDonald was eventually convicted and is serving three consecutive life sentences. The writer Joe McGinniss first got drawn into the story in 1979, when he began work on what became the definitive account of the case, "Fatal Vision." But in the years since, MacDonald has never stopped filing appeals, and several high-profile writers have raised questions about whether he might be innocent after all. McGinniss, largely silent on the topic for years, finally rebuts them all in this compelling follow-up to his 1983 bestseller.

To this day, provocative questions still swirl around the murders: What would cause a seemingly happily married man to slaughter his family so viciously, with a wooden club, knives, and an ice pick? Who were the drug-crazed hippies who MacDonald insisted broke into his house and committed the crimes? Did the government and the military truly suppress evidence that could prove MacDonald’s innocence? And what about the mysterious and deeply troubled Girl in the Floppy Hat?

Forty-three years after the murders, the controversy lives on. MacDonald, now a gray-haired sixty-eight-year-old, continues to attract supporters, most recently acclaimed filmmaker Errol Morris, whose recent book casts doubt on the conviction. The ruling on MacDonald’s latest motion for a new trial is due in early 2013, but as McGinniss makes clear in this fascinating, authoritative book, his guilt is undeniable.