And in terms of current Canadian clients, no one has as high a profile as former CBC Radio host Jian Ghomeshi, charged with four counts of sexual assault and one count of overcoming resistance by choking.
Henein is no stranger to cases involving sexual assault allegations. She was part of the legal team responsible for getting former Nova Scotia premier Gerald Regan acquitted in 1998 of sexual assault related charges. And she successfully defended junior hockey coach David Frost, who was found not guilty in 2008 on all four counts of sexual exploitation against two former players.
What her legal strategy will be when it comes to defending Ghomeshi is anyone's guess. Henein said very little Wednesday at the Toronto courthouse, where, minutes earlier, her client had been released on $100,000 bail. Standing beside Ghomeshi, and surrounded by a crush of reporters and cameras, she indicated she would do all of her talking in the courtroom.
But in a lecture at the University of Windsor law school back in 2010, Henein spoke about the anatomy of the defence narrative. She said that "the importance of developing your narrative starts from the moment the client walks into your office."
"It drives everything that you do, your analysis of the law, your comments to the media, your approach with experts and witnesses. It defines your cross-examination and your examination," she said.
"Each question you ask, you have to advance your theory. Each witness and each exhibit, each conversation you have with the Crown, is about advancing the fabric of the defence narrative."
Henein's colleagues are effusive in their praise of her legal skills and work ethic. That Ghomeshi was able to overlook a joke she made at his expense last month during a gala dinner may speak volumes about her reputation as one of the top criminal lawyers.
"She is as fine a criminal lawyer as this country has," said Toronto lawyer Peter Griffin. "She is smart, creative, dogged and eminently resourceful." She has "terrific judgment," he said, and "trained with the best."
The best being Canadian legal legend Edward Greenspan's law firm, where the Osgoode Hall Law School graduate eventually became a partner. There, she would work on some of the country's highest-profile cases, including the Frost and Regan cases.
Started own law firm
But she would later start her own firm, Henein and Associates and eventually team up with Scott Hutchison, a former Crown attorney whom she had previously battled in court, to form Henein Hutchison.
In 2011, when she made Canadian Lawyer's list of the top 25 most influential lawyers, Henein was described as "a key go-to lawyer for high-profile accused in Toronto."
That reputation was solidified following her defence of former Ontario attorney general Michael Bryant. Bryant had been charged with criminal negligence causing death and dangerous driving causing death in the case of bike courier Darcy Allan Sheppard. But Henein, whom Bryant described as the best barrister he ever met, was able to get all charges dropped in 2010.
"She's universally well-regarded by every player in the criminal justice system," said Toronto lawyer Jonathan Rosenthal, who is vice-president of the Ontario Criminal Lawyers Association. "She thoroughly investigates every possible avenue of a defence. You need look no further than her representation of Michael Bryant."
'No-nonsense defence lawyer'
In a review of Bryant's book 28 Seconds: A True Story of Addiction, Injustice, and Tragedy, the Ontario law magazine Precedent described Henein as a "top notch no-nonsense defence lawyer who is the "real star" of the book.
Meanwhile, the biography on her firm's website says she has argued at all levels of court, including the Ontario Court of Appeal and the Supreme Court of Canada. She was also past president of the Advocates' Society.
Ontario lawyer Peter Cronyn, also a former president of the Advocates' Society, said Henein has a "razor quick mind," describing her as "fearless and brilliant" and very strategic in how she handles her cases.
"She's very strong in terms of cross-examination. She gets to the point quickly. Because she's as smart as she is, she doesn't waste time getting to where she needs to get to."
Cross-examining alleged victims of sexual assault is a tricky endeavour for defence lawyers, but Cronyn said Henein will know "when it's appropriate to be aggressive and when it's appropriate not to be."
However, Rosenthal cautioned that even though Henein is thoroughly gifted, her defence will still be handicapped by Ghomeshi's prior statements on social media.
"She can only play the hand that's been dealt to her. It's not like you just hire Marie Henein and she waves a magic wand and the charges go away."