It could be even harder to determine who stole $500 million dollars worth of art masterpieces nearly three decades ago from the Isabella Stewart Gardner Museum now that evidence has gone missing, according to The Boston Globe.  
In 2010, the FBI decided to analyze duct tape and handcuffs used on museum guards. But the Globe says those items have disappeared. The FBI, however, tells WGBH that a DNA analysis was completed on unspecified evidence.

Stewart Gardner spokeswoman, Kathy Sharpless, says only that the museum's security expert is making progress.

"Since we increased the reward a couple of weeks ago, we have dozens and dozens of new leads," Sharpless said. "Anthony Amore continues to work on this case day in and out following up every lead. He’s working hard. We want the paintings back." 

Thanks to the combined efforts of Amore and the FBI, which is searching as far afield as Europe and Asia, Sharpless says the Museum is confident of getting them back. The reward was recently increased from $5 million to $10 million dollars for recovery of the masterpieces.