Jury selection is underway in the murder trial of a Colorado man who is accused of pushing his wife off a cliff.

The judge in the case reportedly told 50 prospective jurors that the case "will be a doozy."

Prosecutors say Harold Henthorn pushed his wife, ophthalmologist Dr. Toni Henthorn, to her death at Rocky Mountain National Park during an anniversary hiking trip in 2012.

Henthorn, who has pleaded not guilty, claims his wife fell and there were no witnesses.

He was charged after police discovered that he had a map of the area with an X near the spot where his wife fell. Prosecutors believe Henthorn's motive was a million-dollar insurance payout. 

Henthorn's first wife died amid unusual circumstances in 1995, but authorities in Douglas County ruled the death accidental. 

Attorneys Whitney Boan and Chip Merlin discussed the case this morning on "Happening Now." Boan said prosecutors have an uphill battle to prove guilt in this case, arguing that the evidence is circumstantial. 

Merlin said prosecutors will argue that Henthorn had motive and opportunity, and will question his credibility. 

Henthorn's first wife died while the couple was changing a tire on the side of the road and the SUV fell on top of her. 

Boan said prosecutors will need strong witnesses to take the stand and bolster their argument that Henthorn was intent on collecting insurance money in the death of his first wife. 

Watch the discussion above. 

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