For nearly four years, Waco has been buzzing about what happened to Kari Baker, the pretty, popular wife of the young Baptist minister Matt Baker. It was the subject of a Texas Monthly cover story I wrote in March 2008 (“The Valley of The Shadow of Death”). Did Kari, despondent over the death of her young daughter from a brain tumor, commit suicide by overdosing on sleeping pills? Or did Matt come up with a malicious but brilliant plan to murder her in order to be with a 24-year-old single mother named Vanessa Bull who had been attending his church?

I tried to keep the article as balanced as possible. After police initially declared Kari Baker’s death a suicide, Kari’s parents, James and Linda Dulin, launched their own investigation and later persuaded a justice of the peace to change Kari’s death to “undetermined.” As part of their investigation, they came across evidence suggesting Matt was a sexual predator who for years had tried to seduce young women, sometimes going so far as to sexually assault them. A new police investigation began and Matt Baker was arrested in September 2007. But prosecutors realized there was not enough evidence to convict him—the original police investigation was completely botched—and he was never indicted. Matt was released from jail and began talking to reporters (including me), insisting he was innocent, that he had always loved Kari, and that he never had anything but a friendly, platonic relationship with Vanessa.

And that seemed to be that—one of the state’s great unsolved mysteries. For me, the big unanswered question was Vanessa, who is the daughter of a Baptist minister of music who once worked in the same church with Matt. She had told police early on that she had had no romantic relationship with Matt prior to Kari’s death, and that she knew nothing about the circumstances regarding Kari’s death whatsoever. I kept thinking she knew more than she was telling. But she continued to keep her mouth shut. And as long as she did, the case was going nowhere.

Then, this past spring, the Waco media picked up rumors that Vanessa had appeared before a grand jury for about thirty minutes and that she reportedly had been given immunity from prosecution for anything that might come out in her testimony. A few days later, the grand jury indicted Matt for murder. It is fair to say that Waco’s jaw collectively dropped.

The trial finally began this week, and in opening arguments, prosecutor Susan Shafer told the jury that Vanessa would be testifying about her relationship with Baker—“how he brought her into his marital bed and how Matt Baker killed Kari,” Shafer said. People in the courtroom gasped. This was the stuff of Perry Mason—a surprise witness, telling all. More to come…

The Waco Tribune-Herald is live-blogging the trial. You can follow along here.