July 31-August 2, 2014 — He’s the man at the center of the Virginia trial of the century that could be dubbed “sex, lies and gifts.”

And Wednesday, Jonnie Williams came out swinging in testimony that could land former Gov. Bob McDonnell and his wife, Maureen, behind bars for decades.

It’s clear the verdict hinges on whether the jury believes the smooth-talking snitch Mr. Williams, or the now-tarnished Mr. McDonnell, once considered a rising GOP star with a squeaky-clean image.

Mr. McDonnell, 60, is the first Virginia governor to be criminally indicted in the Commonwealth’s 226-year history.

The former first couple is accused of essentially selling the governor’s office in exchange for promises to promote Mr. Williams’ dietary supplement Anatabloc that he and his company touted as able to mitigate the causes of Alzheimer’s disease.

Prosecutors promised Mr. Williams, the former Star Scientific CEO, immunity in a $10 million securities fraud probe for telling his side of the story.

In riveting testimony, Mr. Williams alleged Mr. McDonnell was well aware he was greasing his wife’s palms with loans and pricey gifts and shopping trips.

In exchange, Mr. Williams testified, Mrs. McDonnell promised him her husband would use the governor’s office to promote the Anatabloc supplement.

“He’s the bread winner in the house, and I’m not writing his wife checks without him knowing about it,” Mr. Williams told the jury of Mr. McDonnell’s involvement in the scandal.

Mr. Williams said he eventually told the governor, “I just wanted to make sure that you know about this,” and the governor responded, “Thank you.”

He testified Mrs. McDonnell told him the former first couple was on the verge of bankruptcy and needed fast cash and other gifts.

Prosecutors say Mr. Williams gave the McDonnells more than $165,000 in secret gifts and cash to boost his product.

Mrs. McDonnell’s defense team painted a far different picture of the couple in its opening statement Tuesday.

They said the McDonnells’ marriage was on the rocks and Mr. Williams used his charm to woo the attention-starved former first lady.

Defense attorneys allege Mr. Williams manipulated Mrs. McDonnell into aiding his company.

They said she was not a public official and should not be held to the same scrutiny as her husband.

Mr. Williams stepped down as CEO of Star Scientific in late 2013 as the company faced a federal securities probe and shareholder lawsuits alleging trumped up claims for Anatabloc.

This is not the first time Mr. Williams has been accused of engaging in shady business dealings.

He is alleged to have skipped town when his eyeglass business in Fredericksburg was about to go belly-up in 1981, leaving creditors in the lurch.

Between that time and the Star Scientific fiasco more than two decades later, Mr. Williams is alleged to have profited through the promotion of nearly a dozen other companies, most of which are defunct.