Investigators found female DNA on a fragment of one of the bombs used in the Boston attack, according to anonymous law enforcement sources speaking to CNN and other news outlets. While that news might be encouraging to those engaging in bullish speculation about other possible collaborators working with the Tsarnaev brothers, it doesn't really mean anything on its own.
The DNA, one source told CNN, could be from any woman who touched any component of the pressure cooker bombs at any point. It could also be from a victim. Or, it could be from Tamerlan's widow Katherine Russell, or their 3-year-old daughter. But even if it is one of Tamerlan's immediate family members, it would do little to prove that they were directly involved in the marathon bombings.
As Justin Peters previously explained over at Slate's Crime blog, some lawmakers took to the Sunday morning talk shows this past weekend and emphasized the FBI's investigation into other "persons of interest" in the Boston attacks—arguing, essentially, that the brothers must have at least had some training to build and plant the bombs they used. But it doesn't look like there's really any evidence at this point to suggest that others were involved in that way.
The female DNA, perhaps, is evidence that the federal investigation beyond the brothers is ongoing. But as the New York Times explains, authorities aren't focusing on possible accomplices or connections to organized terrorist groups. What they are probing is whether anyone else had knowledge of the attacks beforehand, or helped them destroy evidence.
That's bound to keep scrutiny on Russell, who said in a statement after the attacks that she was completely in the dark about her husband's plans. No one seems to be taking seriously the idea that Russell, who has been cooperating with FBI investigators, worked as an accomplice. But Russell will likely face continuing questions, for the time being at least, on what she did or didn't know.