Prosecutors in the retrial of Karen Read questioned investigators this week in the high-profile case, while lawyers defending Ms. Read worked aggressively to raise doubts about the investigators’ work.

The prosecution has now spent three weeks presenting its case. It remains unclear when they will wrap and defense lawyers will take over.

Ms. Read, 45, is charged with killing her boyfriend, a Boston police officer, by hitting him with her S.U.V. in a snowstorm in January 2022. Her first trial ended in a mistrial last July when jurors could not agree on a verdict.

The retrial is unfolding in the same courthouse in Dedham, Mass., south of Boston, and has again drawn strong interest from across the country. Many who have followed the case closely remain convinced that Ms. Read’s boyfriend, John O’Keefe, was assaulted at a late-night party in suburban Canton, Mass., and that the police framed her for his murder.

Ms. Read dropped him off at the party after the couple had been out drinking, but she did not stay. Her lawyers have argued that others at the party left Officer O’Keefe for dead in the front yard.

Red plastic fragments in the snow

Over several days of testimony, Yuriy Bukhenik, a sergeant with the Massachusetts State Police, described the earliest steps in the investigation, including the seizure of Ms. Read’s car hours after Officer O’Keefe’s body was discovered early on Jan. 29.