By Dylan Tokar

A senior U.S. Justice Department official who helped supervise investigations into major white-collar crime and the agency's response to the opioid crisis will depart in July, the agency said.

Brian Benczkowski, the head of the department's criminal division, oversaw a number of high-profile cases, including the prosecution of Mexican drug cartel leader Joaquín "El Chapo" Guzmán and a probe into Goldman Sachs Group Inc.'s role in an embezzlement and money-laundering scheme involving Malaysian sovereign-wealth fund 1Malaysia Development Bhd., or 1MDB.

His decision to leave was voluntary and had been in the works for some time, according to an internal memo announcing his departure, which was provided by the Justice Department.

"It truly has been the honor of my professional career to serve at the department once again, and to lead the men and women of the criminal division," Mr. Benczkowski, who previously served in the Justice Department as chief of staff to former Attorney General Michael Mukasey, said in a statement.

Mr. Benczkowski, who is 50 years old, was nominated to serve as an assistant attorney general by the Trump administration in 2017, but his confirmation was delayed over concerns Democrats had about his lack of experience as a prosecutor and work he did in private practice for a Russian bank with ties to Vladimir Putin. Although he had previously served in supervisory roles at the Justice Department, Mr. Benczkowski had never worked as a line prosecutor. He was narrowly confirmed more than a year after his nomination.

He later became embroiled in controversy surrounding a phone call President Donald Trump's had with Ukrainian President Volodymyr Zelensky.

In August 2019, the inspector general for the intelligence community and acting director of national intelligence both referred allegations by an anonymous whistleblower to the Justice Department, claiming Mr. Trump had used U.S. aid to Ukraine to pressure Mr. Zelensky to investigate Democratic presidential rival Joe Biden and his son.

Mr. Benczkowski's division reviewed a transcript of the call to evaluate whether Mr. Trump had violated campaign finance law. It decided he hadn't and declined to open a formal investigation.

As head of the criminal division, Mr. Benczkowski oversaw perhaps the largest team of white-collar prosecutors in the country. His portfolio included the division's fraud section, which is responsible for enforcement of the U.S. Foreign Corrupt Practices Act, an antibribery law.

With Mr. Benczkowski at the helm, the fraud section secured a number of large settlements with multinational corporations over their use of bribes to win business, including an agreement with Ericsson AB that resulted in the telecommunications-equipment maker paying more than $1 billion in fines.

The fraud section also announced several policy shifts related to how it prosecutes corporations. One policy, which became known as the Benczkowski memo, laid out the Justice Department's practices for selecting monitors -- third parties who serve in watchdog roles overseeing a company's compliance with the terms of a Justice Department settlement.

Mr. Benczkowski also oversaw criminal prosecutions of a very different nature, including the department's ramped-up efforts to battle the nation's opioid crisis. To do so, he pushed for the use of special technology by prosecutors in cases where such tools traditionally hadn't been employed.

In 2018, Mr. Benczkowski helped form a task force that used data analytics and traditional law enforcement techniques to identify doctors and other medical professionals who were involved in the illegal distribution of opioids in the Appalachian region.

Drawing on state and federal prescription and medical billing data, the Justice Department says it has been able to step up enforcement against the overprescription of opioids in the U.S.

Write to Dylan Tokar at dylan.tokar@wsj.com