A man accused of killing a Loudoun County man and his mother was released from jail Thursday after Loudoun prosecutors dismissed two murder charges against him. But Loudoun sheriff’s deputies launched new searches of the man’s home and the homes of two of his family members Wednesday night, and the man’s lawyer said his client is still a target of the investigation.

Rishi Manwani, 32, and his mother, Mala Manwani, 65, were found shot to death in their Aldie, Va., home on Jan. 31. Mala Manwani worked as a tax accountant for an information technology company in Falls Church, which reported that she hadn’t come to work, Loudoun sheriff’s officials said, and when deputies checked her residence they found the double homicide. Both victims had been shot multiple times. Rishi Manwani was selling oxycodone out of his home, according to court records. Investigators said later they suspected the drug activity as a possible motive for the slayings.

In March, Loudoun deputies arrested Brian K. Welsh, 38, of Herndon, Va. He was charged with two counts of murder. Welsh had been a friend and customer of Rishi Manwani, according to a search warrant affidavit written by Loudoun Detective Alonzo Perry. Perry wrote that .22-caliber Gemtech bullet casings were found at the crime scene, and that Welsh owned a .22-caliber pistol. The Virginia state crime lab told Loudoun investigators that the casings at the scene matched casings fired from Welsh’s gun. Deputies had seized Gemtech bullets from Welsh’s house, his attorney said.

But the day before a preliminary hearing for Welsh on Thursday, investigators learned that the bullets taken from the Manwanis’ bodies did not match Welsh’s gun. At the preliminary hearing, prosecutors moved to dismiss the case. Loudoun Commonwealth’s Attorney Jim Plowman released a statement saying that the new ballistics information “requires further substantial investigation in a number of areas,” and that the sheriff’s office had “reacted swiftly and has already begun investigative efforts.”

Thomas B. Walsh, Welsh’s attorney, said that included three search warrants served Wednesday night, before Welsh’s release. He said investigators believe that Welsh or a family member had modified the suspected murder weapon after the shootings to replace the barrel and thus give test bullets a different pattern of grooves than the original bullets. The searches occurred at Welsh’s home in Fairfax County, his father’s home in Loudoun County, and his mother’s home in Orange County, Perry’s affidavit states.

“Their case is weak,” Walsh said. He said prosecutors dismissed the charges “because they realized, as I said all along, that the bullets do not match the gun.” He said his client told him the gun suspected of being the murder weapon “hadn’t been fired in years.” Walsh said one of the detectives admitted at an earlier hearing that the bullets didn’t match.

A recent report by the National Institute of Standards and Technology noted that simply comparing one bullet to another, or one casing to another, under a microscope is a subjective method open to misinterpretation. “Bullets and cartridge cases that are fired from different guns might have similar markings,” the authors wrote in February, “especially if the guns were consecutively manufactured. This raises the possibility of a false positive match, which can have serious consequences for the accused.” The report described a new three-dimensional scan of cartridge cases with a much lower likelihood of false positives.

Walsh has also argued that his client’s DNA does not match DNA found at the scene. He said Rishi Manwani’s wallet was found at the scene, emptied of cash, with Manwani’s DNA and an unidentified contributor. He had been seeking further DNA investigation before the dismissal of the case. “The DNA analysis eliminates my client,” Walsh said. “So they decided to step back and continue to investigate.”

A Loudoun sheriff’s spokesman declined to comment on the case Friday.