The bad news: A case about fish that went all the way to the Supreme Court may ultimately let a couple of potential witnesses off the hook.
They are small fish, accused of snatching Tsarnaev's backpack and laptop from his dorm room as authorities closed in on their college friend.
But a Supreme Court ruling on Wednesday means they could walk away free, which would leave prosecutors with no leverage for their testimony.
It looked like the friends -- Dias Kadyrbayev
and Azamat Tazhayakov
, along with a third friend, Robel Phillipos
-- were in a heap of trouble and had little choice but to turn against their "bro," Jahar, as they called Tsarnaev. Kadyrbayev and Tazhayakov are awaiting sentencing in solitary confinement, while Phillipos is under house arrest.
They all faced long prison sentences if they couldn't cut a deal with the feds.
Yates is the captain of a commercial fishing boat called the Miss Katie. He faced 20 years in prison after being convicted of destroying evidence that he had caught undersized red grouper in the Gulf of Mexico. In his case, the evidence was the grouper. How did he destroy it? He threw it overboard.
The high court, led by Ruth Bader Ginsburg, instead tossed Yates' conviction overboard. Writing for the majority, Ginsburg noted that tossing fish back into the Gulf bore little resemblance to the document-shredding frenzy at Enron that inspired the law Yates was accused of breaking, the 2002 Sarbanes-Oxley Act
It was a split decision, 5-4, with Chief Justice John Roberts and Justices Stephen Breyer, Sonia Sotomayor and Samuel Alito in agreement.
As Ginsburg noted in her opinion, the law makes it a felony to "knowingly alter, destroy, mutilate, conceal, cover up, falsify, or make a false entry in any record, document, or tangible object with the intent to impede, obstruct, or influence the investigation."
At issue was what, under this particular law, should be considered "a tangible object." The court determined that Sarbanes-Oxley was written to protect investors and restore confidence in the financial markets after Enron's collapse.
In this case, Ginsburg said, "tangible object" means financial records, not grouper.
"A fish is no doubt an object that is tangible; fish can be seen, caught, and handled, and a catch, as this case illustrates, is vulnerable to destruction," Ginsburg noted. But, she added, to expand the definition of a tangible object to include all things would cut the law "loose from its financial-fraud mooring."
Ginsburg ruled that the shredding law only covers objects used to record and preserve financial records, not "any and every object found on land and sea."
So what's the connection to Tsarnaev? The same law was used to win convictions against his two college friends, Kadyrbayev and Tazhayakov. Does the Supreme Court's decision mean the backpack and laptop, like the grouper, are not covered by this law? Could their convictions be tossed overboard?
Phillipos was charged with and convicted of a different offense: lying to federal investigators. He attended high school with Tsarnaev and bought marijuana from him, according to his lawyers. He acknowledged being present when the laptop and backpack were taken from Tsarnaev's dorm room.
His lawyers portrayed Phillipos as a passive stoner bystander who was "high out of his mind" at the time.
He might have been the smallest fish, but if the other two friends walk, he could be the only one left on the hook, said one of his lawyers, Susan Church. She says he doesn't know much, and the feds have shown little interest in him as a witness.
All three were present when Tsarnaev's laptop and backpack were removed from his dorm room at UMass-Dartmouth three days after the bombing. The backpack was wrapped in a trash bag and tossed in a dumpster behind an apartment complex in New Bedford. It was later found in a landfill.
Investigators found the laptop when they searched the apartment Kadyrbayev and Tazhayakov shared.
Tazhayakov was tried last year and found guilty; he's awaiting sentencing. His lawyer, Nicholas Wooldridge, did not return CNN's phone calls or email. He told local reporters that he was buying a bottle of Champagne but keeping it corked for now.
Wooldridge also portrayed his client as a passive bystander. He tried to shift the blame to his client's roommate, Kadyrbayev, who exchanged texts with Tsarnaev the evening of April 18, 2013:
Kadyrbayev: u saw the news?
Tsarnaev: Yea bro, I did
K: for real?
T: I saw the news... Better not text me my friend Lol
K: u saw yourself there? Ahaha ... hahaha
T: If yu want yu can go to my room and take what's there. But ight bro Salam aleikum
K: whats wrong with you? haha ;)
T: Can't right now bro
Kadyrbayev pleaded guilty about a month after Tazhayakov was convicted and is the only one of the friends to publicly acknowledge a plea deal with federal authorities. Under terms of the deal, he'll receive no more than seven years in prison.
He testified at Phillipos' trial and has indicated he's willing to testify against Tsarnaev as well. His lawyer, Robert Stahl, has not returned reporters' phone calls.
The court has not disclosed the official witness list -- said to include more than 500 names -- so it is difficult to say for sure whether the government planned to call any of Tsarnaev's three college friends to the stand.
Their testimony could connect Tsarnaev to the laptop, which authorities allege was used to download jihadist literature and instructions on how to build pressure cooker bombs "in the kitchen of your mom." The backpack contained hollowed-out fireworks casings and a thumb drive.
As they await sentencing, their court dates keep getting pushed back. To experienced courthouse eyes, that's a telltale sign they're cooperating, or at least talking about cooperating.
The judge in Kadyrbayev and Tazhayakov's cases said late last year that he was watching to see how the Supreme Court ruled in the Yates case.
It's common practice for federal prosecutors to dangle a deal, watch a witness sing, and then vouch for him or her at sentencing to shave off a few years of hard time.
But these two would have little incentive to cooperate if their convictions are overturned and long federal prison sentences are no longer hanging over their heads.
No cameras are allowed at the Tsarnaev trial. But CNN's Ann O'Neill will be there every day. Think of her as The 13th Juror
, bringing insights here weekly. And follow @AnnoCNN on Twitter daily.