Excerpts from Stephanie Birkitt's private diary make up the centerpiece of Robert Halderman's alleged plan to extort $2 million from David Letterman.
Halderman (who is also known as Joe Halderman) threatened to expose his inter-office affairs if he did not comply, according to law enforcement officials.
The writings of Stephanie Birkitt was presumably not meant for the eyes of former lover Letterman, or a more recent one, CBS News producer Halderman.
But pages copied from her diary are critical to the police investigation.
Stephanie Birkitt, 34, was an assistant on The Late Show with David Letterman and frequently appeared on camera herself, along with the host, in comedy skits.
She was also once his lover, according to her own diary (another woman, Holly Hester, is alleged to have had an affair with Letterman while he was still at NBC).
Later, she became romantically involved with Robert Halderman. The couple lived together in his Norwalk, Conn., home until August, when they reportedly split.
Stephanie had once worked on 48 Hours Mystery, the show where Halderman was a well respected producer. CBS News has suspended him since his arrest.
Robert Halderman apparently copied pages from Birkitt's diary before they broke up, using them together with e-mails and other information in a package left in Letterman's limo that was intended to extort money from him.
Halderman's attorney, Gerald Shargel, said Monday that Letterman is a master manipulator and only telling one side of the story, while the charges against his client are "so obviously out of character to the point of not making any sense."
After he pleaded not guilty in a Manhattan court last week to a count of attempted first-degree grand larceny, Halderman is currently free on bail.