In 2008 Perego found a DNA connection between Joseph Smith, the first prophet of The Church of Jesus Christ of Latter-day Saints, and King Niall of the Nine Hostages, an Irish warlord of the fifth century. This connection was found using STR profile values.
The STR profile assigns a number value to certain small sections on a person's Y chromosome. An STR profile looks like a long list of numbers. One person's number values can be compared section by section with another person's values. The closer two people's STR values align the more likely they are connected.
"We know exactly was the Joseph Smith and Smith family Y chromosome STR profile looks like," Perego said. "As accurate as if I had Joseph Smith next to me and I would get a swab from him. It's not guesswork."