A year ago, New York State Police Investigator Joseph Becerra was working the highest-profile case of his career. Becerra was trying to crack the unsolved 1982 disappearance of Kathie Durst and resolve suspicions that Robert Durst, the millionaire Manhattan real estate man she was unhappily married to, made it happen.

Today, the Durst case remains unsolved, but Becerra isn't working it. Instead, he investigates fatal accidents on the New York State Thruway and more mundane cases, like Hudson Valley parents who supply beer kegs for their underage teenagers' parties.

Becerra's reassignment may be partially the result of a book written about the case, according to author-journalist Matthew Birkbeck. At least that was the impression Birkbeck came away with after being grilled by a New York State Police internal affairs investigator for 90 minutes at a pancake house in Stroudsbourg, Penn., on May 29.

The officer wanted to know where Birkbeck got his information, and specifically how much Becerra told him.

"They're looking to basically get something on him. It's all so petty," Birkbeck told Courttv.com Thursday.

Birkbeck enjoyed unparalled access to Becerra and many witnesses in the case, and his book provides insights and details only people closely associated with the investigation could know. A quick read, even at 300 pages, "A Deadly Secret: The Strange Disappearance of Kathie Durst" goes deep inside both the 1982 investigation and Becerra's re-investigation without giving away Birkbeck's inside sources.

Birkbeck's publisher, Penguin Putnam, confirmed that New York State police subpoenaed any state police documents that Birkbeck may have submitted with his manuscript. The company replied that there weren't any, a spokesperson said.  

Birkbeck said he told the investigator that Becerra never broke any rules and the book was culled from information supplied by dozens of people.

"Whenever I pressed him about evidence, he was like, 'I can't go there,'" Birkbeck said.

The internal affairs investigator, who sipped coffee as he referred to three or four pages of typed questions he brought with him, seemed mostly interested in learning who supplied the writer with information that portrayed Westchester District Attorney Jeanine Pirro in a less than favorable light, Birkbeck said.

Westchester County, N.Y., District Attorney Jeanine Pirro

Though long a suspect in the minds of police and Kathie Durst's friends and family members, Robert Durst has not been charged with any crime in connection with his former wife's disappearance (he divorced her secretly in 1990). If criminal charges ever arise from the case, Pirro's office will be the one to prosecute.

Birkbeck's book makes a case that Pirro, an elected official who answers to voters, wants the spotlight from the Durst investigation to shine on her and her alone. The book gives most of the credit to Joe Becerra, a 39-year-old career police officer, and friends of Kathie Durst who would not let the case die.

Acting on a tip that turned out to be inconsequential, Becerra reinvestigated almost every aspect of the case and, according to Birkbeck's book, concluded that police initially made wrong assumptions that hampered the case. Among other things, they never got a search warrant for the South Salem house even after learning about Robert Durst's odd behavior and Kathie Durst's intense unhappiness in what police were told was an abusive marriage.

Pirro did not return calls. Her press office promised to get back to a reporter but did not.

Becerra did not return calls either, which did not surprise Birkbeck.

"He's a decorated cop. What's he going to do? He's got Pirro after him," Birkbeck said.

When Becerra was taken off the case, new investigators began knocking on the same doors he knocked on after picking up the huge investigation file for the first time in 1999.

One of those doors belonged to Ellen Strauss, a Connecticut attorney who was close friends with Kathie Durst.

Since Becerra was transferred, Strauss said she has been reinterviewed by two assistant district attorneys from Pirro's office and no less than four state police investigators. Strauss said she is concerned that Becerra's departure was payback for the book and that the recent re-investigation of a case he had well under control could create a paper trail that could harm any future prosecution of Durst.

Strauss said she has not been asked anything about Becerra by the internal affairs investigators but is concerned that resources that could be used to solve the mystery surrounding her friend's disappearance are being diverted.

"It's harmful to the case because, whether it is right or wrong, she has called into question the integrity of the investigating officer. That's all legally discoverable," Strauss said. "It's pure ego and bad karma. It makes her look petty and sad. This policeman did nothing but honor his badge."

Over the years, Robert Durst has issued a reward for information about Kathie Durst and denied knowing anything about her disappearance.

Her family and friends fear she suffered the same fate as Morris Black, an elderly neighbor of Robert Durst's during the eccentric millionaire's time living under an assumed name and sometimes dressed as a woman, in a $300-a-month apartment in Galveston, Texas. Pieces of Black's body, all but his head, were found floating in garbage bags in Galveston Bay in October 2001.

Robert Durst, now 60, has pleaded not guilty by reason of self-defense accident. Jury selection in his murder trial is scheduled for Aug. 25.