A married Manhattan corporate lawyer’s double life came crashing down after he was arrested for smacking his mistress in the face and threatening to kill her, according to court papers.

@FunkFlex

Steven Guynn, who has handled billion-dollar deals involving big-bucks clients around the world, allegedly punched gal pal Jeannette Schaefer after flying into a rage over breakfast last week in the tony New Canaan, Conn., home he shares with his wife.

For years, Guynn had showered his 41-year-old mistress with gifts — and even tried to start a business with her. But on the morning of March 14, their secret romance turned violent.

Guynn allegedly slapped her four times “in a punching manner” to the right side of the head, leaving a bruise under her left eye, according to the police report.

It wasn’t clear what set him off.

“Jeannette . . . stated that Steven also forcefully grabbed her left arm, leaving a bruise,” cops wrote.

Two days later, Guynn visited Schaefer’s apartment in New Canaan, the police report said. What happened during that visit was unclear from court papers. But cops allege that Schaefer tried to call 911 from her apartment and that Guynn stopped her.

When cops finally spoke to Schaefer later that evening, she showed them her bruises.

“Jeannette stated that Steven is controlling and abusive and that she is in fear of him,” police said.

After taking Schaefer’s report, cops went to Guynn’s home and confronted him just inside his front door.

Guynn was reluctant to speak, taking several seconds to answer each questions and finally stating that “he did not care to discuss his private relationships with us,” the cops wrote.

They arrested him after he confirmed that he had had a “physical altercation” with Schaefer two days earlier in his house.

The court papers say that, besides last week’s attack, Guynn also beat Schaefer last year.

In the May 2011 incident, Guynn assaulted Schaefer “with approximately 30 hits to her stomach, face and upper body” and threatened her life, the police report says.

Schaffer backed up the claim with photographs, police say.

One of Schaefer’s friends confirmed that story to police, say court papers.

Guynn and Schaefer carried on their affair for two years behind the back of Guynn’s wife, Kristie, a writer and editor whose byline appears in Mormon church publications

The Guynns are both graduates of Mormon-guided Brigham Young University in Utah. Steven was class valedictorian.

The couple has two daughters who are also Brigham Young grads, Kristie Guynn’s Facebook page says.

Because Guynn was married, Schaefer told cops, “the relationship between her and Steven . . . is confusing,” court papers said.

According to cops, he regularly bought her “all sorts of things” — gifts, money, trips.

“Jeannette stated that Steven will stay with her at [her] apartment on occasion and that she has stayed at his residence when his wife is out of town,” the cops wrote.

The two set up a business called Raw Flora, built around Schaefer’s interest in eco-travel and nutritional supplements. Corporate records list the company’s official address as Guynn’s home and say he and Schaefer are its only officers.

“All of our products, EcoTours and programs have been strategically developed to support community projects, educate participants on sustainability efforts, offset carbon emissions, and contribute to scientific research,” says the company’s Web site.

Guynn’s fellow partners at the worldwide King & Spalding law firm were aware of his legal woes — but declined to say whether he was officially in hot water.

“We take this issue seriously, and we are working to understand the facts,” the firm said in a statement.

Guynn declined to speak at his New Canaan home yesterday.

Schaefer also refused comment.

Guynn, who is free on $30,000 bail, joined King & Spalding in early 2010 and has enjoyed a globe-trotting legal career.

King & Spalding’s Web site says he has “led more than $150 billion in transactions in the US, Europe, Asia, the Middle East and Latin America.”

He helped the Kuwaitis with a $3 billion investment in Citigroup and advised them on the progress of the US financial crisis, the law firm says.

Guynn also helped the Kuwaitis with a $4 billion co-investment in Dow Chemical alongside financial wizard Warren Buffett’s company, Berkshire Hathaway.

Guynn’s experience in Latin America could have been a big help in the venture with his girlfriend. According to Raw Flora’s Web site, the firm is planning a 10-day eco-tour this summer in Peru’s Manu Biosphere Reserve.

“We offer unique and life-altering eco tours into the rain forests of South America,” Raw Flora claims. “Experience the untamed wilderness. Discover where wild foods, superfoods, raw water and medicinal plants thrive in perfect balance of pristine nature.”

Raw Flora also claims to sell “the highest-quality therapeutic, wildcrafted and organic products available. Every product is formulated with the utmost concern for potency, purity, biological vitality, and effectiveness.”

WRITTEN BY: LAUREL BABCOCK and BILL SANDERSON & FULL STORY HERE