Sen. Cory Booker, D-N.J., is calling on Senate Judiciary Committee Chair Lindsey Graham, R-S.C., to hold a hearing into Immigration and Customs Enforcement’s “egregious and appalling abuses,” including the widespread use of solitary confinement.

In a letter to Graham, Booker, who sits on the Judiciary Committee, referred to solitary confinement as a “form of torture” and cited a recent investigation by the International Consortium of Investigative Journalists, The Intercept, NBC News, and four other reporting partners into ICE’s use of solitary confinement. Our reporting, which included a review of more than 8,400 reports describing placement in solitary confinement from 2012 to early 2017, found that ICE uses isolation as a go-to tool, rather than a last resort, to punish vulnerable detained immigrants.

“ICE’s own policy seems to recognize the dangers of solitary confinement.”

“The news stories detail numerous examples of individuals placed in confinement without justification, which prompted a whistleblower to come forward to shine a light on these abuses,” wrote Booker, referring to Department of Homeland Security employee Ellen Gallagher, who quietly raised the alarm about ICE’s use of solitary confinement for four years before going public in interviews with the reporting consortium. While different carceral systems use varying terms to describe solitary confinement — ICE calls it “segregation” — it is generally understood to be the practice of holding individuals in isolation with no human contact for at least 22 hours a day.

“ICE’s own policy seems to recognize the dangers of solitary confinement,” Booker continued. “It appears ICE has been consistently violating its own policy on the use of solitary confinement.”

His letter to Graham comes on the heels of a letter from Sen. Elizabeth Warren, D-Mass., to the acting director of ICE, demanding answers about the agency’s use of solitary confinement and extensively citing our investigation. Sen. Richard Blumenthal, D-Conn., another member of the Judiciary Committee, also called for a hearing into ICE’s use of solitary in response to our investigation last month. The panel’s Democrats do not have independent authority to schedule a hearing, hence the request to Graham.

Booker, in his letter, said that a Judiciary Committee hearing about ICE would give the panel a chance to interrogate “grossly unsanitary conditions at detention facilities,” as well as to gather more information about forthcoming immigration raids that President Donald Trump “flippantly alluded to” on Twitter last week. The president, after announcing that the agency would begin to round up “millions” of immigrants this week — a logistically impossible endeavor — on Saturday put the ICE operation on hold.

Graham, an anti-immigrant hard-liner and apologist for the Trump administration’s harsh policies, convened a committee hearing — at Democrats’ request — in March to investigate Customs and Border Protection for its actions at the southern border. Graham used the hearing as an opportunity for fearmongering about migrants seeking asylum in the United States. The CBP, like ICE, falls under the umbrella of the Department of Homeland Security.

The oversight hearing on CBP was not enough, Booker wrote. “In order to fully address the scope of ICE’s serious and egregious violations, the Committee must convene an oversight hearing. It’s becoming increasingly clear that ICE has become nothing more than a lethal weapon in the Trump administration’s war on immigrants and communities of color, and we cannot be silent.”

Booker’s harsh stance against ICE in the letter to Graham is in line with the tack he’s taken on the presidential campaign trail, where he’s been a staunch critic of the agency’s policies. In February, he, along with other 2020 hopefuls Warren, Sen. Kamala Harris, and Sen. Kirsten Gillibrand, voted against a spending bill, citing ICE. At the time, Booker said that bill would give ICE and CBP “hundreds of millions of additional dollars with little oversight or appropriate guardrails.” In April, he reintroduced legislation to enact protections for detained immigrants.

Booker has also been an outspoken advocate of the rights of prisoners throughout his federal career. At the same time, he’s remained close to a party boss in his home state who oversees a jail that serves as an immigration detention center and is rife with abuses, drawing the ire of local progressives.

As Politico reported on Tuesday, Booker will be in New Jersey on Friday for a $2,800-per-person fundraiser co-hosted by Essex County Executive Joseph DiVincenzo. In that role, DiVincenzo oversees the Essex County Correctional Facility in Newark, which has a $40 million per year contract with ICE — and was called out for poor conditions in two DHS Inspector General reports just this year.

Twenty-one progressive organizations last week sent a letter to Booker calling on him to cancel the fundraiser, Politico reported. “I believe that Booker wants to make sure that the funnel of money keeps coming through, and that’s why he’s supporting Joe [DiVincenzo] right now,” Carrine Murphy, a paralegal who is critical of county jails’ contracts with ICE, told Politico.

In February, the Office of Inspector General identified a number of issues at the jail, including food safety issues, with “potentially contaminated food being served to detainees.” One example noted “a detainee in segregation said the food was so bad that he had started a liquid only diet and was considering a full hunger strike.”

Earlier this month, the Inspector General issued a follow-up report building on the same inspection and said that “detainees are placed in disciplinary segregation before the disciplinary hearing panel finds the detainee guilty of the charged offense.”

The facility has reported making improvements in its solitary confinement practices, “including documenting why detainee strip searches were conducted and revising recreation schedules to add additional recreation time,” the Inspector General wrote.

The ICIJ and Intercept investigation found 100 records of placement in solitary confinement at the Essex County jail from 2013 to early 2017. Twenty-seven of those placements were due to disciplinary reasons, while three of them were the result of a suicide risk. Overall, we found at least 373 instances of detained immigrants being placed in isolation because they were potentially suicidal — and another 200-plus cases of people already in solitary confinement moved to “suicide watch” or another form of observation, in many cases in another solitary cell.

Immigration is expected to be a hot-button issue throughout the presidential campaign. Booker and Warren will both participate in the first 2020 Democratic presidential debate in Miami, Florida, on Wednesday night.