Two brothers from the Old Lyme area pleaded guilty Wednesday in New London Superior Court in connection with a series of burglaries in which high quality jewelry, precious metals, antiques, guns and other valuables were stolen from homes throughout the region between 2009 and 2012.

Justin P. Weissinger, 27, and Karl W. Weissinger, 23, each pleaded guilty to three counts of second-degree larceny. The younger brother, who has been free on bond while his cases were pending, also pleaded guilty Wednesday to third-degree assault in connection with a domestic violence incident for which he and the mother of his infant daughter were arrested over the weekend.

Justin Weissinger will be sentenced Aug. 20 to up to nine years in prison followed by three years of probation. Karl Weissinger will be sentenced the same day to three years in prison followed by three years of probation. Both of the brothers accepted plea deals that had been worked out by prosecutor David J. Smith, their attorneys, John Franckling and Jeremiah Donovan, and Judge Hillary B. Strackbein.

The brothers both pleaded guilty under the Alford Doctrine, which indicates they do not agree with the state’s allegations but do not want to risk harsher sentences if convicted at trial.

Matthew L. Hopkins, a Mystic jeweler charged with being in possession of nearly $200,000 in stolen items he purchased from the brothers, is expected to plead guilty on July 30. Resolution of the case means that state police, who seized the stolen items during their investigation, will be able to return the items to the victims, some of whom have attended dozens of the defendants’ court appearances. At the request of Hopkins’ attorney, Michael L. Cozzolino, the judge ordered state police to return to Hopkins items that were seized from him that were not part of the burglary case. Some of the burglary victims are expected to speak at the sentencing, and the Weissingers’ attorneys may call on their mother and others to speak on their behalf.

Justin Weissinger has been incarcerated since he was arrested following a high-speed chase with Montville police in July 2012 that led to the burglary charges. Police said Weissinger had in his possession at the time a .380-caliber pistol that had been stolen from a Salem home and other stolen items. The investigation led state police to a barn on Brush Hill Road in Lyme, where they said they recovered guns stolen during burglaries in East Haddam and Salem, and to the Mystic jewelry store.

While his case was pending, Justin Weissinger served as a key witness for the prosecution at a high-profile home invasion/murder trial in California of three of his fellow former Marines. They were all convicted.

After taking his plea, the judge warned Karl Weissinger, who is being electronically monitored and has a curfew, that he risks going to prison for up to 31 years if he gets arrested again between now and his sentencing date. Following the June 21 domestic violence incident, state police seized a shotgun that Weissinger’s girlfriend said he had asked her to purchase for him at Dick’s Sporting Goods, according to the judge.

“You’re getting a significant break here because of your brother (who will be serving a longer sentence) and the desire to resolve the whole case,” Strackbein said.

k.florin@theday.com