Viral claims have falsely suggested that US citizens cast extra votes in the 2020 US presidential election by using the identities of "dead people".
Social media users allege that a large number of dead persons' ballots have been registered in swing states such as Pennsylvania and Michigan.
US President Donald Trump has continued to assert - without evidence - that the election was undermined by voter fraud.
State officials have repeatedly said there is no evidence of these claims.
Experts have also told Euronews that if there were irregularities, they would not have affected the election result.
There are multiple explanations for why voters can be registered with unusually old birth dates, including software errors and voter confidentiality issues.
The rumour that deceased people cast votes "appears in every election" said Jason Roberts, a professor of political science at the University of North Carolina.
"Once the analysis is done, the vast majority of discrepancies, or things that look like potential fraud, are often discovered to be human error," said Tammy Patrick, senior advisor to the Democracy Fund Foundation, which oversees voting issues in the US.
The false claims
An article by right-wing publication Breitbart News falsely claimed that 21,000 dead voters had been registered in Pennsylvania.
The story was shared by Rudy Giuliani, the former New York City Mayor and Donald Trump’s personal attorney, collecting more than 100,000 likes and shares.
The claim stemmed from when the conservative Public Interest Legal Foundation filed a lawsuit against Pennsylvania’s Secretary of State in October, accusing officials of improperly including 21,206 supposedly deceased citizens on voter rolls.
The complaint was rejected by the court and Pennsylvania Attorney General Josh Shapiro has reiterated that there was no evidence of this alleged fraud.
"The court found no deficiency in how Pennsylvania maintains its voter rolls and there is currently no proof provided that any deceased person has voted in the 2020 election," Shapiro tweeted.
Senior Republicans such as Senator Lindsey Graham and Representative Matt Gaetz, have supported the claim the Trump campaign has "evidence of dead people voting".
“The dead vote appears to have swung overwhelmingly for Joe Biden,” tweeted Gaetz, accusing Democrats of trying to steal the election.
The Michigan Secretary of State's office issued a statement saying the claims were "wrong" and "not accurate".
"We are not aware of a single confirmed case showing that a ballot was actually cast on behalf of a deceased individual", they said.
Where do the rumours originate and what are the facts?
Although extremely rare, people have tried to vote fraudulently for others who have died.
"We may encounter one person or a handful of people that voted in two different states but we have laws against that and those individuals will be criminally prosecuted," said Patrick.
Experts have also stated that when deceased people's ballots are occasionally registered, this is most often when a small number of people have died in the period between when they sent in a mail-in ballot and election day.
Ms Patrick, a former Arizona election official, told Euronews that these rare examples tie into the narrative that dead people are voting.
"If someone votes prior to election day, mails-in their ballot, and then passes away, their ballot packet will be rejected and they will be reported as a 'deceased voter'".
"The general population believes that that means someone was deceased and their ballot was cast, when in fact they were very much alive when they voted."
Absentee ballots cast by Michigan and Pennsylvania residents who die before election day are not counted, but voter rolls can be delayed.
Experts also point out that people who appear to be voting while dead may simply share a deceased person’s name or birthday, and have not updated their administrative records.
"In some counties alone, there are dozens of people with the same name or even date of birth, so the wrong voter history can be selected," said Patrick.
"When we look into allegations of voter fraud, these are the sorts of answers that we find, not that it was in fact fraud."
Patrick also told Euronews that dead people can be unintentionally registered as having voted if another voter's handwriting falls into another row on a signature roster.
"If a signature overlaps into other cells, this triggers the system into believing that two or three people have voted, when it was actually just one very flamboyant voter with a large signature," said Patrick.
Why are some voters registered with unusually old birth dates?
Occasionally, eligible voters in the United States may also submit ballots with unusual birth years that make it appear as if they're impossibly old or deceased.
Roberts told Euronews that a common or default birth date is often entered for voters when none was previously listed for them.
This can happen during the process when states transfer from paper records to an electronic database.
Generic dates like January 1, 1900, are also used in electronic poll books as a default for absentee ballots that arrive on election day.
A 2017 report about duplicate voting from the Government Accountability Institute also suggested that some voter birth dates could also be listed as 1800.
"It is important to note that some state registration systems indicate a missing date of birth by adopting filler dates, such as 01/01/1900, 01/01/1850, or 01/01/1800," the report stated.
In Pennsylvania, some active voters are also listed with unusual birth dates for “confidentiality reasons”, such as if they've been victims of domestic violence, according to the state website.
"There is human error in elections, absolutely no doubt, and there are small examples of people who do try to vote illegally," said Roberts.
"But there is no evidence whatsoever of any sort of voter fraud on any sort of a scale, that would ever affect the outcome of an election".
In some US states the correcting of voting history and analysis of ballots is done in the months after election day.
Patrick says allegations of criminal activity made just days after an election are "ill-founded".
"We need to take the time to review every allegation, because of course because we want to maintain the integrity of the system.
"The misinformation is being spread nationally and globally to try and sew doubt on the outcome and legitimacy of the election."
Election officials in the US, such as the Cybersecurity and Infrastructure Security Agency (CISA), have worked hard to shore up security defences after widespread allegations of interference during the 2016 vote.
"At this point in time, we have not seen any sort of widespread voter fraud," Patrick told Euronews.
"It is not something that happens in abundance in the United States, they are rare and isolated occurrences, and this election has been no exception to that rule."
"It's easy in this day and time for these rumours to fly around," added Roberts, "but when you really get down to the evidence, it's just not there".