The story starts with a list of around 10,000 names posted on Twitter by a Trump-supporting activist.
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We called Roberto Garcia, a retired teacher in Michigan. He told us: "I'm definitely alive and I definitely voted for Biden - I would have to have been dead to vote for Trump."
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Our selection of 31 cases is only a small sample of the 10,000 names on the list, but it has clearly revealed the flaws in the database shared by Trump supporters.
From our investigation it's clear that in almost all of our 31 test cases, the data for genuine voters in Michigan has been combined with records of dead people with the same name and birth month and year from across the United States to yield false matches.
"If the lists are linked based on name and birth date alone, in a state the size of Michigan, you're guaranteed to get false positives," says Prof Justin Levitt, an expert on the law of democracy.
It's known as the birthday problem - the high probability that two students in the same class share the same birthday.