Original post, 1:59 p.m.: As you can see above, federal prosecutors arguing that Dzhokhar Tsarnaev should be executed for his role in the 2013 Boston Marathon bombing have released a July 2013 image of Tsarnaev, then 20 years old, showing his middle finger to a security camera in what appears to be a holding cell. In its Tuesday opening statement as the penalty phase of Tsarnaev's trial began, the prosecution argued that the image demonstrates the convicted bomber's unrepentant, remorseless attitude. Defense attorneys attempted to put the gesture in a less harsh context during testimony Wednesday by introducing the video from which it was taken. Said video also shows Tsarnaev fixing his hair and flashing a peace sign—perhaps indicating that the middle finger was a spontaneous act of boredom rather than a pointed statement.
Update, 2:50 p.m.: Here's the video.
Of note: What some reporters described as a peace sign looks like it could also be a different (and more insulting) gesture.