Boston police are investigating allegations that officers who were assigned to guard the home of a homicide suspect remained inside his apartment, watching television and resting on the couch even before detectives obtained a search warrant.

On Tuesday night, seven hours after Christopher Jamison, 23, allegedly shot Anthony Perry, 22, in Jamaica Plain, officers went inside his Roxbury home and ordered his mother to leave.

After police looked through the apartment to be sure no one else was present, at least two officers remained inside most of the night without a warrant, said Ozell Hudson Jr., a Boston-based lawyer representing Jamison's mother.

When the mother returned to her apartment around noon Thursday, she saw two officers sitting on her couch, Hudson said. Police still had not obtained a search warrant.

"The manner in which this search was done was certainly contrary to established constitutional procedures," said Hudson, who added that he was at the apartment Tuesday night.

Officers have the right to seize a home after a crime if they believe a suspect remains inside or there is evidence they must obtain immediately, according to police and legal specialists. Once they have ensured no one is inside the home, they should stand guard outside and prevent anyone from entering until a search warrant is executed.

Officers can go back in only if they believe someone entered after they seized the home, said Elaine Driscoll, spokeswoman for the Police Department. The policy, which is dictated by the Fourth Amendment assuring right to privacy, also guards against accusations of evidence-tampering, she said.

Driscoll said internal affairs investigators are looking into the allegations Hudson raised.

Dana Curhan, an appellate lawyer in Boston who has handled search-and-seizure cases, said police can go back "if there is some kind of emergency situation where evidence is about to be destroyed or somebody might be in danger."

"Other than that, they pretty much have to wait," he said. "It sounds like an incredible violation of these people's privacy if they're camping out in their living room for two days."

Driscoll said police seized the apartment at 8:29 p.m. Tuesday, obtained a search warrant at 2 p.m. Thursday, and searched it about a half-hour later.

"We apologize to Ms. Jamison for any inconvenience that our presence may have caused," she said. "The legal process required to execute a search warrant can take anywhere from an hour to a couple days. It is our goal to be as expeditious as possible, but being thorough is more important."

Two firearms were found in the apartment after the search warrant was obtained, said two law enforcement officials with knowledge of the investigation.

Former prosecutors and defense lawyers said it is unusual to take so long to obtain a search warrant. Police only need to provide probable cause to persuade a judge or magistrate to issue a search warrant, they said. Most warrants are issued within hours.

"You don't need proof beyond a reasonable doubt," said Robert M. Griffin, former chief of prosecutions for Suffolk Superior Court and a Boston defense lawyer. "You want to get the warrant as soon as possible. The longer you wait, the more potential for lost evidence."

Driscoll declined to describe the investigators' probable cause because the homicide is now before a grand jury. She described the case as complex because homicide investigators were receiving new information every hour that they needed to include in the affidavit.

Hudson said whatever police obtained during the search could be tainted by their earlier presence inside the apartment. Hudson said he was at the apartment for three hours Tuesday night and saw officers going inside several times, locking the door behind them. One young patrolman refused to go inside, saying he believed he should stand guard at the door, Hudson said.

"I told him, 'You're the only one getting it right,' " Hudson said.

Legal specialists said it is would be almost impossible to prove police searched the home before the warrant was obtained. It could, however, affect the way jurors perceive police during the trial, Griffin said.

"Whether or not it's going to result in a negative verdict for the Commonwealth, nobody can answer that question," he said. "But it's enough to stain the credibility of the police."

Maria Cramer can be reached at mcramer@globe.com.

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