The police, who initially thought it was an accidental death, did not immediately dust for fingerprints, or collect DNA. Nor did they secure items in the bathroom for evidence. They took no notes and spoke to only a few neighbors. They never searched Mr. Covlin’s apartment or the building’s common areas for evidence. They even allowed the family’s rabbi to clean the bathroom with peroxide, eliminating any evidence of blood.

Mr. Gottlieb said in closing arguments on Monday that there was no way to determine who had murdered his client’s wife, largely because detectives had botched the investigation.

“It is impossible to know beyond a reasonable doubt what happened to Shele Covlin, how it happened and why it happened,” he said.

Because Ms. Danishefsky Covlin was buried without an autopsy, the cause of death was undetermined for several months. But as suspicions grew regarding Mr. Covlin, the family had her body exhumed, and in April 2010, a medical examiner determined that she had been strangled, her neck squeezed with such force it fractured the hyoid bone, causing bleeding in her right eye.

Still, it took five more years before prosecutors had enough evidence to arrest and charge Mr. Covlin, a self-proclaimed martial arts expert, with her murder.

Ms. Danishefsky Covlin had been married to Mr. Covlin for 11 years, and before her death had confided in family members and close friends about his erratic and abusive behavior, according to testimony and evidence presented at trial.

She wrote to her sister, Eve Karstaedt, in January 2009 that she was “very scared that at some point in the future all his anger and rage may result in something bad happening — he really can’t control his temper.”