“She notified him and there certainly didn’t seem to be any notion of surprise – just a report that ‘you’re being watched.”
Katherine Russell Tsarnaeva's family is still insisting that she knew nothing, but if this report pans out, then she didn't just passively accept Islam, she actively engaged with it and may have known about the plot all along. At the very least this would make her an accessory after the fact.
Dzokhar Tsarnaev told interrogators that the information that set in motion the series of events leading to Tamerlan’s death and Dzokhar’s apprehension came in a phone call from Katherine Russell Tsarnaeva to her husband. “She notified him and there certainly didn’t seem to be any notion of surprise – just a report that ‘you’re being watched,’” said one official with knowledge of the investigation.
Tsarnaev had seen the photographs and videos distributed by the FBI on television and called her husband to give him a heads up.After receiving that phone call, authorities believe, Tamerlan decided he could not continue to hide from law enforcement and triggered the brothers’ bizarre flight from authorities – a wild chase that included the murder of an MIT police officer, a convenience-store robbery, a carjacking, shootouts with police officers, the death of Tamerlan and the capture of Dzokhar.
You're being watched is not "What the hell is going on" or "This is crazy, let me call a lawyer and we can help prove you didn't do it." Those would be expected responses. This is closer to the range of, "They know it's you."
It's likely that Tamerlan's illegal activities didn't begin with the attack. The family was getting government assistance while Tamerlan worked odd jobs, but at the same time there seemed to be plenty of money. The obvious explanation, and this would be somewhat typical, is that Tamerlan was engaged in criminal activities, and it's unlikely that his wife didn't know about them.
We already know that the younger brother was involved in all sorts of shady side businesses. It's likely that the older brother was too. And if Tamerlan trusted his wife's conversion, then he would have told her, as a good Muslim, what his plans are. Jihadists in Europe routinely told their wives what they were doing.