HBO's three-part docuseries "The Pet Cemetery Murders," subtitled "A Ghost Story," airs its final episode on Sunday, October 25, closing out a series about one of Louisiana's strangest cold cases. Directed by Philip Cairney and produced with Lightbox, the series premiered October 11 and revisits the 1985 killing of pet cemetery owner Dorothy Lou Thompson, according to Wikipedia.

The show leans into the supernatural. The legal story underneath it turns on something more ordinary, a witness with a criminal record, no physical evidence and a prosecution that chose a sure conviction over a risky trial.

A body in the river

Thompson ran the Azalea Original Pet Cemetery in Toca, in St. Bernard Parish near New Orleans. She disappeared from her home on April 13, 1985, Biography reported. On May 2, fishermen found her body in the Mississippi River in Plaquemines Parish, weighed down with chains. She had been strangled with a plastic bag secured over her head with wire.

Investigators focused early on Brandon Nodier, who had worked as the cemetery's groundskeeper. Thompson had sued Nodier over her 14 acres, saying the land was taken through a fraudulent sale. She vanished about 10 days before that case was set for court, WVUE Fox 8 reported at the time of his indictment.

Sheriff Jack Stephens said Nodier was a prime suspect from the start, but there was not enough evidence to arrest him. The case went cold for more than 25 years, and Hurricane Katrina later washed away much of the evidence investigators had, The A.V. Club noted in its review.

The witness who said he was haunted

The break came from people who said Thompson's ghost would not leave them alone. In 2009, an anonymous caller who described being haunted by her told police Nodier had confessed. In 2012, James J. Tregler, Nodier's former assistant groundskeeper, contacted authorities from behind bars and said he had watched the killing, according to Biography.

Tregler said Nodier had visited him and threatened him to stay quiet. In April 2012, Nodier surrendered and was charged with second-degree murder. "The motive was his strong desire to possess Dorothy Thompson's land," Col. John Doran said then, Fox 8 reported.

Why it ended in a plea

The case never reached a jury. In July 2014, Nodier pleaded guilty to manslaughter under a plea agreement and was sentenced to 10 years in prison by Judge Perry Nicosia of the 34th Judicial District, The Advocate reported. Under the parole rules in effect in 1985, he could expect to serve less than five years, according to his defense attorney.

Both sides described it as a compromise. Defense attorney Pat Fanning said, "They didn't have a great case." Prosecutors were relying largely on Tregler, whose criminal record made him a gamble in front of a jury. Sheriff James Pohlmann said he would have liked to see Nodier spend the rest of his life in prison, but noted there is "always a risk of going to trial with little evidence," according to Fox 8.

Judge Nicosia told Nodier he had received a bargain. "You got away with this horrible act of violence for a long time," the judge said, according to The Advocate.

A plea to a lesser charge is a trade. A defendant trades the risk of a far longer sentence for certainty, and the state trades the risk of an acquittal for a conviction. In a cold case built on one witness, that math looks different for both sides than it does in a case with physical evidence.

When a case rests on a single witness, the alternative can be a split jury and a second trial. Read what happens after a hung jury for how that plays out. It is the kind of case the Two Taps legal panel of Daniel Rosenberg, Michael Dye and Lloyd Golburgh takes apart on the show.

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Two Taps News stories summarize reporting and the analysis discussed on Two Taps and Friends. They are not legal advice. Read our standards.