Raymond Clark III, who was charged with strangling 24-year-old Annie Le, of Placerville, Calif., would plead guilty in New Haven Superior Court, public defender Joseph Lopez said Tuesday.
Lopez would not specify the charges but said it was part of a plea deal.
"We anticipate a change of plea on Thursday," Lopez said.
"This appears to be in the best interests of our client."
Prosecutor John Waddock said there was a "substantial likelihood" of a change of plea from Clark, who had pleaded not guilty. He declined further comment.
Le's body was found stuffed behind a research lab wall on the day she was supposed to get married in New York in September 2009.
The crime drew intense national media attention and prompted the New Haven Register to print a rare extra edition announcing Clark's arrest.
Le and her fiance, Jonathan Widawsky, planned to marry on Long Island and honeymoon in Greece. Instead, family and friends held a memorial service at which Le was remembered for her academic success, sense of humor, ambition, love for shoe shopping and love for her fiance.
Le's relatives were grateful for the support they have received from the community and from law enforcement, family spokesman Kevin Eckery said Tuesday. They didn't want to comment on the guilty plea because it hasn't happened, he said.
"But they're very conscious of the sad fact that no plea and no sentence will bring Annie back," he said.
Le was a doctoral pharmacology student who worked on a team that experimented on mice as part of research into enzymes that could have implications for treatment of cancer, diabetes and muscular dystrophy.
Clark, 26, was a high school baseball and football player whose duties included cleaning mouse cages and the floors of the lab.
Clark, who has been in prison on $3 million bail, has pleaded not guilty to murder and felony murder, which each carry a sentence of 25 to 60 years in prison upon conviction.
Felony murder is alleged when someone dies during the commission of a felony, such as robbery, burglary, kidnapping and sexual assault, or an attempted felony. Under Connecticut's felony murder law, prosecutors don't have to prove that a killing was intentional.
Police have said a green-ink pen under Le's body had her blood and Clark's DNA on it. Police said Clark signed into the secure building with a green pen the day Le disappeared.
Authorities have said they took plastic door panels and carpeting with "blood-like stains" from the car in which Clark was riding during the hours after Le's disappearance.
They had also said DNA from Le and Clark was on a bloody sock found hidden in a ceiling.
Court papers describe a bloody crime scene and Clark's efforts to scrub floors. Investigators say Clark tried to hide a box of cleaning wipes that later was found to have traces of Le's blood.
Clark had scratches on his face and left arm that he said came from a cat, investigators wrote in court papers.