I looked through all the comments but still haven't seen an answer to an obvious limitation(that is posed near the end of the article): Where are they getting

I looked through all the comments but still haven't seen an answer to an obvious limitation(that is posed near the end of the article): Where are they getting their library of heartbeats from? I'm sure the CIA is collecting, but being able to positively ID someone with their heartbeat is useless unless you already have a verified record of their heartbeat. Imagine the case of finding an elusive person (such as Saddam Hussein or Osama Bin Laden), somebody has to go collect a verified sample BEFORE an assassination takes place. But if you are in a position to collect a sample of someone's heartbeat and you KNOW that it's the right person through some other verifiable means (you need to know if you actually got OBL instead of a body double), then what does this really get you? You already had some trustworthy source, and you can probably use this previous source to verify that you assassinated the right person. So this heartbeat ID tech may be more accurate and robust compared to facial recognition, but it's less useful in actuality. We already have verified pictures of most adults in the world via passports and driver's licenses and such, which makes facial recognition a ton more useful in real life. The problem that this heartbeat tech "solves," the ability to ID someone with great accuracy, is hamstrung by the fact that the elusive people we have the greatest need for an ID like this won't have their data available. For non-elusive people we can already find them by getting their picture and address out of a database. But you can bet the CIA realizes this limitation and will work diligently over the next few years to get heartprints of Kim Jong Un, Vladimir Putin, and other notorious figures at every public appearance so that they can slowly build a library that will be useful down the road.