With the disclosure yesterday of new evidence in the killing of a high-profile real estate agent, Linda Stein, lawyers defending the chief suspect said they will seek to prove that police obtained a false confession from Natavia Lowery. A medical examiner’s report January 11 found that blood from an unidentified man was discovered in a bathroom sink, mixed with some of Stein’s blood, Ms. Lowery’s lawyer, Ronald Kuby, said.

The report also showed that, while blood was splattered throughout Stein’s apartment in the attack, no blood was found on the clothing that Ms. Lowery, 26, was wearing when the assistant allegedly bludgeoned her employer to death inside her Fifth Avenue apartment in October, Mr. Kuby said.

Ms. Lowery’s lawyers, Mr. Kuby and David Pressman, said the disclosures add to mounting evidence that, after about 12 hours of interrogation inside a Manhattan precinct house, Ms. Lowery was coerced into confessing that she beat Stein to death with a piece of exercise equipment.

Barbara Thompson, a spokeswoman for the Manhattan district attorney, Robert Morgenthau, said prosecutors would deal with the issue during Ms. Lowery’s trial.

“We’re talking about a tiny speck of blood,” Ms. Thompson said. “There is nothing to suggest that the blood came from the murderer.”

The blood found in the sink was barely detectable, a law enforcement source said.

Even if the amount of blood discovered is small, several defense attorneys said the forensic evidence is a good sign for the defense.

“Prosecutors of late have used all this DNA and ‘CSI’-type evidence to make cases. Leave it to Ron Kuby to use it to break a case,” a high-profile defense lawyer, Arthur Aidala, said.

In a letter addressed to the state Supreme Court justice presiding over the case, Micki Scherer, Ms. Lowery’s lawyers said the male blood found in the sink presumably belongs to the killer.

Although Mr. Kuby said no forensic evidence ties Ms. Lowery to the killing, she confessed to the murder in a written statement to detectives.

Mr. Kuby plans to argue that detectives coerced Ms. Lowery into making a false confession. The fact that Ms. Lowery told detectives that Stein blew marijuana smoke in her face, though autopsy results showed Stein did not have the drug in her system, and that the alleged murder weapon, a “yoga stick,” has not been found, show that police misled Ms. Lowery into falsely confessing, Mr. Kuby said.

Ms. Lowery is expected in Manhattan Criminal Court tomorrow for a hearing on pending motions.