(CNN) —  

Justice Department Inspector General Michael Horowitz, who is testifying before Congress on Wednesday about his new report on the early stages of the Russia investigation, has built a reputation as a thorough investigator who has waded into some of the more controversial issues of the last few years.

Horowitz, who was appointed to his post by former President Barack Obama in 2012, is testifying before the Republican-controlled Senate Judiciary Committee about the report released on Monday, which concluded the FBI was justified in opening the Russia investigation in July 2016 and that top FBI officials weren’t motivated by political bias against President Donald Trump.

Horowitz’s report also debunked some conspiracy theories that Trump has promoted for years, including his claim that US intelligence planted spies in his campaign.

But Horowitz, who has a lengthy history as an oversight professional, has already received a number of criticisms from the President and Attorney General William Barr, who have suggested the inspector general’s report reached the wrong conclusion. His findings on foreign surveillance and the FBI process on Wednesday also received fierce pushback from Chairman Lindsey Graham, one of Trump’s strongest supporters in Congress, who has already made comments about the report that go farther than its conclusions.

Horowitz highlighted during his testimony the lengths his office went to in order to conduct the probe into the Russia investigation called “Crossfire Hurricane.” CNN reported earlier this year that his office conducted more than 100 interviews as part of its probe, including with Christopher Steele, the author of a dossier of unverified intelligence reports about the Trump campaign.

A career in oversight

As the Justice Department’s watchdog, Horowitz oversees more than 450 employees “whose mission is to detect and deter waste, fraud, abuse, and misconduct” at the department, according to his biography on the Department of Justice’s website.

Horowitz’s office’s blockbuster report into the FBI’s handling of the investigations of Hillary Clinton, released in 2018, excoriated former FBI Director James Comey for “extraordinary and insubordinate” moves that, along with the revelation of anti-Trump text messages exchanged between Peter Strzok, a former senior counterintelligence officer, and Lisa Page, an attorney, did lasting damage to the FBI’s reputation. The 2018 report, however, ultimately concluded that Strzok and Page’s actions were not motivated by political bias.

Horowitz also released a report in August finding that Comey violated FBI policies when he retained and leaked a set of memos he took documenting meetings with Trump in 2017. The report said Comey set a “dangerous example” for FBI employees in an attempt to “achieve a personally desired outcome.”

In addition to his DOJ job, Horowitz has also served since 2015 as the chair of the Council of the Inspectors General on Integrity and Efficiency, an organization created “to address integrity, economy and effectiveness issues that transcend individual Government agencies and aid in the establishment of a professional, well-trained and highly skilled workforce in the Offices of Inspectors General,” according to its website.

Prior to becoming DOJ’s inspector general, Horowitz served for six years as a commissioner on the US Sentencing Commission, which aims to set fairer sentencing guidelines.

Horowitz also worked as an assistant US Attorney for the Southern District of New York from 1991 to 1999, “where he was the Chief of the Public Corruption Unit and a Deputy Chief of the Criminal Division,” according to his biography, which said he was awarded for his work investigating police corruption.

The inspector general has also twice held stints at prestigious private law firms, first with Debevoise & Plimpton near the beginning of his career, and later at Cadwalader, Wickersham, & Taft LLP between 2002 and 2012, according to his biography.

Horowitz received his bachelors degree from Brandeis University and holds a law degree from Harvard.

CLARIFICATION: This story has been updated to reflect that Senate Judiciary Chairman Lindsey Graham fiercely reacted to Horowitz’s findings.