An NBC News fact-check may give Massachusetts Senator Elizabeth Warren the cover she needs to further explain her repeated refusals to take a DNA test that would prove the Native American ancestry she has claimed to have.

DNA tests are not widely accepted as proof of tribal citizenship — in part because the DNA could not show a specific tribe, only some genetic markers from Native people — and are more unreliable for Native Americans than for other ancestral regions. https://t.co/D9KFhDaeN8 — NBC News (@NBCNews) July 6, 2018

Warren’s heritage has been a question mark for nearly a decade, since her 2012 Senate campaign against Republican Scott Brown. Reports surfaced that she had claimed minority status on official forms from 1986-1995, and that another Harvard professor had boasted that she was Native American. Her campaign was unable to offer conclusive proof, but Warren maintained that her mother had always told her it was a part of their heritage.

Being Native American is part of who our family is and I’m glad to tell anyone about that. I am just very proud of it.

President Donald Trump has often attacked Sen. Warren, casting doubt on her claims of Native American ancestry, suggesting that she used the claims to advance her own career and daring her to “prove it” by taking a DNA test.

But according to the NBC report, even if she did take a DNA test, the results could be inconclusive.

Independent genealogist Megan Smolenyak explained, “The reality is she could take a DNA test and have Native ancestry and have it not show up because it depends on which branches of the family tree it’s in and how far back. That test is very good for finding stuff out going back five, six generations. If you have one great-great-great-great-grant-great grandmother, it’s not going to show.”

Donald Trump Jr. wasn’t buying it, saying that it was just another convenient excuse.