Transcript for Ballot Watch: Signature verification could snarl massive mail ballot count
And tonight still days away from the election and a record nearly fifty million Americans have already voted by mail shattering the total of 33 million in 2016. But before the crush of ballots can be officially tallied election workers must first and verify the signatures are to take a closer look at just how that's done. And why some worry that too many ballots could be wrongly thrown out. Here's Devin Dwyer was knights valley watch. As millions of mail ballots pour in all eyes are on the signatures. Election officials in Washington DC showing ABC news how they analyze handwriting to make sure marked ballots match real people. Each person you scan it and there's. There file signature comes up and you have to go look at it and. And it's not doubt song. We will have a if there balance we've given the chance to sign it and spirit. The verification is an essential step before any mail in votes can be counted. Signature he could not. Every hour. Matters and pounds. And sometimes that little can can really make an impact more than and other times we need to make sure that every eligible American and has a ballot counted on even if they didn't cross that heat or forgot to dot NI. An ABC news analysis of the last two election cycles found more than 750000. Mail in ballots were thrown out nationwide. Many for not having a valid signature or for arriving late. During this year's primaries more than 500000. Were tossed for the same reasons. Individuals who are inexperienced with mail voting I tend to have their ballots rejected at higher rates and I and that's an important thing right now of course because so many people. Are new to voting by mail. Researchers say signature errors disparate. Proportionately trip up younger voters and minority voters and rarely reflect attempted fraud. Sadly what we have found is that. Signatures may very for all kinds of reasons someone's he someone may have had a stroke somebody maybe it's moving too fast. And so in those instances were really pushing officials to give voters. Notice and an opportunity to cure any issue that you may have identified. While several states have detailed guidelines for signature matching others do not leading some experts too worried that a subjective analysis of the voters handwriting. Could unfairly compromised their vote. Staffer under trained they're under resource and they'll be under tremendous pressure to get results quickly and they're moving through. Thousands or millions of signatures in the state and bear on B signatures very quickly. Them. Mistakes can happen experts say there's a 97%. Likelihood that a ballot rejected for an unsuccessful signature comparison should have been counted. It's one reason why Pennsylvania Supreme Court last week unanimously ruled that no ballots can be thrown out this year over an alleged signature mismatch. There are Republicans seniors they would say wait a sack. Shouldn't we be checking the signatures to make sure they're real. If you're lying on my EE UA EC driver's license or photo ID your client for our mail and out application you need to go to so security. There are already all that's in the crops I heard that builder. Mandel lacks that I wait. Action is the. Remember if you attempt to make voter fraud act of comedy and you will be prosecuted. But states that do you analyze mail ballot signatures may soon be in the spotlight especially if the election is close there will be hardest and challenging a signature verification and signature is in. The days following the election. In many states we prepare it sells for now. A brewing potential legal battle reminiscent of the one in Florida twenty years ago. An election in turmoil a presidency in the ballot. A nation weight but this time instead of hanging and dimpled chads it could come down to slant. And slow and then stopped and line orientation and connecting. Our letter is. For ABC news live. I'm Devin Dwyer in Washington. So potentially some different scrutiny of the ballots this time around our thanks to DeVon for that.
This transcript has been automatically generated and may not be 100% accurate.