The department also announced limits on federal officers’ use of widely criticized policing tactics.WASHINGTON — The Justice Department has opened an investigation into allegations of unconstitutional abuses of prisoners in Georgia, a sweeping civil rights inquiry that could force the state to carry out a federally mandated overhaul.The department also separately limited whether and how federal law enforcement officers can use tactics that have been widely criticized for their role in the deaths of Black people at the hands of the local police, including neck restraints like chokeholds and unannounced searches for evidence.The moves, announced on Tuesday, broadly address issues of violence in law enforcement and incarceration that have become a rallying point for criminal justice advocates and led to protests and civil unrest around the country.The Georgia investigation was prompted by documentation of violence in prisons across the state. During a riot last year at Ware State Prison that played out on social media, hundreds of inmates took over the building, set fires and took guards hostage, resulting in damage and myriad injuries.At least 26 people died in 2020 by confirmed or suspected homicide in Georgia prisons, and 18 homicides, as well as numerous stabbings and beatings, have been reported this year.“Under the Eighth Amendment of our Constitution, those who have been convicted of crimes and sentenced to serve time in prison must never be subjected to ‘cruel and unusual punishments,’” Kristen Clarke, the head of the Justice Department’s civil rights division, said in announcing the investigation during a virtual news conference.Ms. Clarke said that dangerous conditions in the state’s prisons, including “contraband weapons and open gang activity,” seemed to be exacerbated by many systemic factors. She cited staffing shortages and high employee turnover, policy and training issues and a lack of accountability for misconduct. But she said that the department had not reached any conclusions about the allegations it was investigating.The investigation will focus on prisoner-on-prisoner violence and include an open inquiry by the department into the sexual abuse of gay, lesbian and transgender prisoners by staff members and other prisoners.Should investigators in the Justice Department’s civil rights division and Georgia’s federal prosecutors determine that prisoners are subject to a pattern or practice of constitutional violations, the agency could place the state’s Department of Corrections under a consent decree, a federally mandated overhaul that is overseen by the courts and outside monitors.The Justice Department has recently used consent decrees to impose overhauls on state prisons in Virginia and New Jersey.Last year, it sued Alabama over the condition of its prisons, accusing staff members of violating the Constitution by allowing a systemic culture of excessive force against inmates to grow. Alabama has fought being placed under consent decree.Georgia officials denied on Tuesday that they had systematically violated the rights of inmates, the determination that is often the precursor to a consent decree.“The Georgia Department of Corrections is committed to the safety of all of the offenders in its custody,” Lori Benoit, a department spokeswoman, said in a statement.She added that the department’s commitment to safety “includes the protection of lesbian, gay, bisexual, transgender and intersex (L.G.B.T.I.) prisoners from sexual harassment, sexual abuse and sexual assault.”The Justice Department also announced a policy that prohibits federal law enforcement officials from using chokeholds and so-called carotid restraints unless they are authorized to use deadly force. It also limited the circumstances under which federal law enforcement could conduct unannounced, or so-called no-knock, entries.The policies apply only to federal officers, so they do not change state and local policing rules.But they directly address practices that gained notoriety after high-profile episodes that fueled public criticisms of the police and their use of force, including the 2014 death of a Staten Island man named Eric Garner after a police officer put him in a prohibited chokehold during an arrest. Cellphone recordings of Mr. Garner gasping “I can’t breathe” catalyzed the national Black Lives Matter movement and the officer, Daniel Pantaleo, was fired, though the Justice Department declined to bring civil rights charges against him.Last year, Louisville police officers fatally shot Breonna Taylor, a Black medical worker, during a botched raid on her apartment, helping set off months of wide-scale demonstrations over racial injustice and policing. Whether the officers announced themselves beforehand was in dispute, bringing scrutiny on the practice of no-knock raids.The Justice Department’s policy changes stemmed from a review of law enforcement practices led by the deputy attorney general, Lisa O. Monaco.“It is essential that law enforcement across the Department of Justice adhere to a single set of standards when it comes to ‘chokeholds,’ ‘carotid restraints’ and ‘no-knock’ entries,” Ms. Monaco said in a statement. “This new policy does just that and limits the circumstances in which these techniques can be used.”Federal officers are generally required to knock, identify themselves and their purpose, and demand entry before going into a building. The Justice Department said they were allowed to depart from the practice only if officers had reason to believe that announcing themselves could put them in danger.