As calendar year comes to a close, sizing up the Mueller investigation originally appeared on abcnews.go.com

If special counsel Robert Mueller’s probe into Russian meddling in the 2016 election was once a cloud hanging over the Trump administration, the near-daily headlines coming out of the high-profile investigation post-midterm election might rightly be described as a downpour.

With recent developments in the special counsel’s cases against President Donald Trump’s former longtime personal attorney, former campaign chairman and former national security adviser, Mueller and his team of prosecutors are showing no signs of slowing down as the new year approaches.

(MORE: The Russia probe: A timeline from Moscow to Mueller)

Over the course of his 19 months as special counsel, Mueller has indicted 33 individuals and three businesses. Of those indicted, seven people have pleaded guilty, four people have been sentenced to prison, and one person has been found guilty at trial.

Here is an update on where the Russia probe stands:

Michael Cohen preparing for prison

PHOTO: Michael Cohen walks out of federal court in New York, Nov. 29, 2018. (Julie Jacobson/AP) More

The president’s longtime personal attorney and fixer has transitioned from one of Trump’s most fervent defenders to a cooperating witness in multiple probes targeting the Trump family, campaign and related business ventures.

Prior to Cohen’s sentencing in the Southern District of New York for crimes including campaign finance violations, tax evasion and lying to Congress in early December, the special counsel acknowledged his help with the Russian investigation in a sentencing memo. In an exclusive interview with ABC News’ George Stephanopoulos, Cohen said “the special counsel stated emphatically that the information that I gave to them is credible and helpful. There’s a substantial amount of information that they possessed that corroborates the fact that I am telling the truth.”

In court documents filed earlier this month, prosecutors wrote that Cohen provided “information about attempts by other Russian nationals to reach the campaign” and “useful information concerning certain discrete Russia-related matters core to [our] investigation.”

(MORE: President Trump says Michael Cohen should go to prison; praises Roger Stone's 'guts' for saying he won't testify)

The office of the special counsel in August referred Cohen's case to the Southern District of New York, where federal prosecutors implicated Trump in a scheme to silence women who alleged during the 2016 campaign that they had extramarital affairs with him before he became president, according to court documents -- a revelation Cohen first raised during a plea hearing in August.

Trump has denied the affairs.

Federal prosecutors in New York were not as pleased with the cooperation Cohen completed, with one attorney stating at Cohen's sentencing hearing in December that Cohen “didn’t come anywhere close to assisting this office in an investigation," and adding that “the charges portray a pattern of deception, of brazenness and of greed.”

In addition to charges brought by the Southern District of New York, Cohen pleaded guilty to the special counsel's charge that he lied to Congress.

Cohen has offered to continue aiding various investigations, including the special counsel’s probe, even after learning his sentence, telling Stephanopoulos, “If they want me, I am here and I am willing to answer whatever additional questions that they may have for me.”

Michael Flynn's sentencing delayed

PHOTO: Former White House National Security Advisor Michael Flynn leaves the Prettyman Federal Courthouse following a sentencing hearing in U.S. District Court, Dec. 18, 2018 in Washington. (Chip Somodevilla/Getty Images) More

Retired Army Lt. Gen. Michael Flynn has been cooperating with the special counsel's office for much of the past year. Flynn was slated to be sentenced in late December, but after Judge Emmet Sullivan laced into the former Trump national security adviser during his sentencing hearing, his attorneys and the special counsel prosecutors agreed to delay.