KYIV — In the lengthy cast of Ukrainian prosecutors starring in the political scandal engulfing the Trump administration, Gyunduz Mamedov hasn't received much of the spotlight.

Figures such as Viktor Shokin and Yuriy Lutsenko — both former prosecutors general of Ukraine — stand out for providing what Rudy Giuliani, a lawyer working for President Donald Trump, has described as "substantial evidence" to support his back-channel Ukraine campaign.

But Mamedov's role was key. He was an intermediary in Giuliani's efforts to press Ukraine to open investigations into former Vice President Joe Biden and the debunked conspiracy theory about the country's interference in the 2016 presidential election, according to documents reviewed and interviews conducted during a collaboration among BuzzFeed News, NBC News and the Organized Crime and Corruption Reporting Project (OCCRP).

The documents and interviews show Mamedov was integral in setting up at least two sets of meetings that are now the focus of congressional investigators pursuing an impeachment inquiry against Trump.

And while Shokin and Lutsenko have been sidelined after being fired in 2016 and 2019, respectively, Mamedov was appointed as a deputy prosecutor general Friday, according to a statement by Ukraine's Prosecutor General's Office (PGO).

Gyunduz Mamedov. Prosecutor's Office of the Autonomous Republic of Crimea / via Facebook

Working in recent years as the lead prosecutor for cases related to the Russian-occupied region of Crimea, Mamedov has largely evaded public attention for his role in the scandal, despite public scrutiny of meetings between Giuliani and other Ukrainian officials, including Lutsenko and Shokin.

But the documents and interviews show that Mamedov's involvement included acting as a go-between for Lutsenko and two Florida associates of Giuliani, Lev Parnas and Igor Fruman, who pleaded not guilty Wednesday to charges that included illegally funding U.S. political campaigns with foreign money.

A July investigation by BuzzFeed News and the OCCRP found that Parnas and Fruman were key middlemen setting up Giuliani with Ukrainian prosecutors.

Mamedov and Hlib Zahoriy, then a Ukrainian lawmaker, accompanied Lutsenko to meetings with Giuliani, Parnas and Fruman in New York on Jan. 25 and 26, according to minutes of the meetings handed to House committees by the U.S. State Department's Inspector General.

The minutes show that Lutsenko furnished Giuliani with a range of unsupported accusations alleging wrongdoing by Biden, his son Hunter, and officials in the U.S. Embassy in Kyiv, including then-Ambassador Marie Yovanovitch.

Both Mamedov and Zahoriy played roles in the meeting, Lutsenko said in an interview in London, where he is apparently studying English and also far from Ukrainian authorities who've launched a criminal investigation into whether he abused his power while prosecutor general.

"They were there as private citizens. Mamedov was one of the people who passed Rudy Giuliani's invitation [to meet] to me," Lutsenko said.

In fact, it was Mamedov whom Parnas and Fruman first approached with the initial proposal for Lutsenko to meet Giuliani, according to Lutsenko and Zahoriy. Mamedov then conveyed that to Lutsenko's staff, Lutsenko said, adding that Mamedov knew Giuliani's associates from his time in the Ukrainian port city of Odessa. The Black Sea port city is where Fruman built up his business network in Ukraine in the 1990s and the early 2000s.

Mamedov also played a role in brokering another February meeting between Lutsenko and Giuliani in the Polish capital, Warsaw, Lutsenko said.

Born in the former Soviet republic of Azerbaijan, the 44-year-old Mamedov, a bald, clean-shaven man with caterpillar eyebrows, cuts a relatively low profile in Ukraine. He declined a request for an interview. The Prosecutor General's Office said in a statement that Mamedov had been promoted based on "significant results" he had achieved as the prosecutor overseeing Crimea.

Mamedov's family is involved at senior levels in Azerbaijan's state-run oil and gas sector, which is heavily controlled by the family of the country's president, Ilham Aliyev.

Fruman and Parnas used their involvement with Giuliani's Ukraine campaign to push their own plan to sell American liquefied natural gas (LNG) to the country.

There's no evidence to suggest Mamedov was involved in furthering Parnas' and Fruman's LNG business plan.

Zahoriy, 43, the then-Ukrainian lawmaker who was also present at the New York meetings in January, is a pharmaceutical company owner who, along with Lutsenko, was politically aligned with former President Petro Poroshenko.

Zahoriy's intended role in the meeting was to act as a translator, Lutsenko said.

"I asked him to go there in case I wouldn't understand something because I was afraid of New York slang. Sometimes Zahoriy talked when Giuliani couldn't understand my English," he said.

Zahoriy told reporters that he was in New York for personal business and had been having breakfast with Lutsenko on the morning of the first of the two meetings — Jan. 25 — when the chief prosecutor asked him to come along. He said that Giuliani and Lutsenko did most of the substantive talking, while the others sat to the side.

Parnas and Fruman struck him as less-than-reputable "adventurists," Zahoriy said.

Like Lutsenko, Zahoriy said the initiative for the January meetings had come from Parnas, Fruman and Giuliani. Mamedov, who does not speak English, was simply an intermediary, he said.

"The role of Mamedov was to connect Giuliani [to Lutsenko] through Fruman," Zahoriy said.

Giuliani for his part has said that it was Ukrainian prosecutors who took the initiative in bringing to him the allegations at the heart of his campaign against Biden.

"This is information that was given to me," Giuliani told Fox News host Sean Hannity in early October.

"I didn't go looking for Joe Biden. The Ukrainians brought me substantial evidence of Ukrainian collusion with Hillary Clinton, the DNC, George Soros, George Soros' company. They put it in my lap," he said.

Giuliani did not respond to a request for comment for this article.

According to their federal indictment, Parnas and Fruman were also working on behalf of a Ukrainian official, who has since been identified as Lutsenko.

Lutsenko did not respond to questions about this role, but Larisa Sargan, the former prosecutor general's spokeswoman, neither confirmed nor denied that he had asked the men to work on his behalf, saying: "I saw [the media reports] but there are 40 million people in Ukraine."