Cash App founder Bob Lee appeared to be snorting cocaine off a knife blade just hours before he was stabbed to death, explosive footage revealed for the first time by his accused killer's defense during their closing statements showed.

"That's the knife," Nima Momeni's defense attorney Saam Zangeneh told jurors in a San Francisco courtroom Tuesday as footage taken just hours before Lee, 43, was stabbed to death on April 3, 2023, was played, Mission Local reported.

The footage showed Lee standing with his friend Bo Mohazzabi outside a club where they'd been drinking that night. Both then bent over and appeared to snort something off a pointed, shining object Lee held in his hand. Lee then dug with the object in what appeared to be a small bag and lifted it to his nose.

"Look at the dimensions. Look at the size. What else could that be?" Zangeneh asked jurors, raising a cutout of the 3.5-inch blade that matched the knife Lee was killed with.

"As long as we have a reasonable theory, you have to find him not guilty," the attorney said. "Unless they could show that our theory is not reasonable, then he's not guilty."

The footage could upend prosecutors' argument that Momeni was the one who brought a knife along when he and Lee drove off together later that fateful night.

Separate footage of the pair leaving the apartment of Momeni's sister Khazar Elyassnia, 38, before the stabbing has been central to the case, and prosecutors argued that it showed Lee had no blade on him before the stabbing.

Prosecutors have argued Momeni stabbed Lee to death in a rage over his sister -- who Lee was reportedly having an affair with -- and had allegedly been sexually assaulted by drug dealer Lee introduced her to.

But Momeni's attorneys claimed a heavily inebriated Lee was the aggressor, and that he sprang at Momeni with the knife over a joke about going to strip clubs rather than spending time with family. They said Momeni was merely defending himself, and that Lee was fatally stabbed as they fought over the blade.

A knife that was taken from the kitchen of Momeni's sister was found at the scene of the stabbing.

During a rebuttal to Zangeneh's closing, prosecutor Omid Talai cast doubt on whether the object Lee held in the video was even a knife, and told jurors the science still backed that Momeni was the killer -- citing forensics finding 99% of DNA found on the handle of the knife that killed Lee came from Momeni, while 98% of DNA on the blade came from Lee.

"Should we believe the defense attorney," Talai said, according to Mission Local. "Or should you believe science and DNA?"

But the new footage also appeared to undercut the testimony of Mohazzabi, who told jurors that he'd overheard Momeni being "aggressive" during a phone call with Lee about his sister that night -- but also that he didn't remember doing any drugs with Lee or seeing him do any that night.

It was just the latest twist in a case that has sent shockwaves through the San Francisco tech world, which remembered Lee as a well-loved, hardworking innovator after his death.

But the case exposed a seedier underbelly of the well-heeled community, with a social scene dominated by swinging sex parties and drug-fueled benders taking center stage.

Jury deliberations are due to start on Wednesday.