In a damning new report by the Smoking Gun, a crucial witness in the grand jury deciding whether to indict former Ferguson, Mo. police officer Darren Wilson is revealed as having fabricated her eyewitness account of the altercation between Wilson and unarmed 18-year-old Michael Brown on Aug. 9. "Witness 40," identified as 45-year-old Sandra McElroy, has a documented history of racist remarks, criminal behavior, and mental illness.

McElroy's testimony has been latched on to by Wilson defenders because of how closely her report matched the embattled police officer's. But as the Smoking Gun points out, the timing of McElroy's interviews with authorities is suspicious: Both her statement to St. Louis police on Sept. 11 and another to Justice Department prosecutors on Oct. 22 immediately followed stories detailing Wilson's account of the day:

McElroy provided the federal investigators with an account that neatly tracked with Wilson's version of the fatal confrontation. She claimed to have seen Brown and Johnson walking in the street before Wilson encountered them while seated in his patrol car. She said that the duo shoved the cruiser's door closed as Wilson sought to exit the vehicle, then watched as Brown leaned into the car and began raining punches on the cop. McElroy claimed that she heard gunfire from inside the car, which prompted Brown and Johnson to speed off. As Brown ran, McElroy said, he pulled up his sagging pants, from which "his rear end was hanging out."

But instead of continuing to flee, Brown stopped and turned around to face Wilson, McElroy said. The unarmed teenager, she recalled, gave Wilson a "What are you going to do about it look," and then "bent down in a football position…and began to charge at the officer." Brown, she added, "looked like he was on something." As Brown rushed Wilson, McElroy said, the cop began firing. The "grunting" teenager, McElroy recalled, was hit with a volley of shots, the last of which drove Brown "face first" into the roadway.

"I know what I seen," she apparently told skeptical investigators. "I know you don't believe me." Her story of how she wound up in Ferguson that day doesn't sound convincing, either:

When asked what she was doing in Ferguson—which is about 30 miles north of her home—McElroy explained that she was planning to "pop in" on a former high school classmate she had not seen in 26 years. Saddled with an incorrect address and no cell phone, McElroy claimed that she pulled over to smoke a cigarette and seek directions from a black man standing under a tree. In short order, the violent confrontation between Brown and Wilson purportedly played out in front of McElroy.

But when she testified before the grand jury charged with deciding whether to indict Wilson, her story changed:

McElroy, again under oath, explained to grand jurors that she was something of an amateur urban anthropologist. Every couple of weeks, McElroy testified, she likes to "go into all the African-American neighborhoods." During these weekend sojourns—apparently conducted when her ex has the kids—McElroy said she will "go in and have coffee and I will strike up a conversation with an African-American and I will try to talk to them because I'm trying to understand more."

McElroy also brought a highly-touted journal with alleged entries penned in the days surrounding Michael Brown's killing. The entry dated Aug. 9 starts, "Well Im gonna take my random drive to Florisant. Need to understand the Black race better so I stop calling Blacks Niggers and Start calling them People."

If McElroy's testimony in Darren Wilson's grand jury proves to have been made up, this will not have been the first eyewitness report she fabricated:

McElroy's devotion to the truth—lacking during her appearances before the Ferguson grand jury—was also absent in early-2007 when she fabricated a bizarre story in the wake of the rescue of Shawn Hornbeck, a St. Louis boy who had been held captive for more than four years by Michael Devlin, a resident of Kirkwood, a city just outside St. Louis.

McElroy, who also lived in Kirkwood, told KMOV-TV that she had known Devlin for 20 years. She also claimed to have gone to the police months after the child's October 2002 disappearance to report that she had seen Devlin with Hornbeck. The police, McElroy said, checked out her tip and determined that the boy with Devlin was not Hornbeck.

In the face of McElroy's allegations, the Kirkwood Police Department fired back at her. Cops reported that they investigated her claim and determined that "we have no record of any contact with Mrs. McElroy in regards to Shawn Hornbeck." The police statement concluded, "We have found that this story is a complete fabrication."

According to the Smoking Gun, McElroy was diagnosed with bipolar disorder at age 16 and has gone untreated for the condition for 25 years. She also has a history of posting racist comments on social media:

An examination of McElroy's YouTube page, which she apparently shares with one of her daughters, reveals other evidence of racial animus. Next to a clip about the disappearance of a white woman who had a baby with a black man is the comment, "see what happens when you bed down with a monkey have ape babies and party with them." A clip about the sentencing of two black women for murder is captioned, "put them monkeys in a cage."

McElroy's YouTube page is also filled with a variety of anti-Barack Obama videos, including a clip purporting to show Michelle Obama admitting that the president was born in Kenya. Over the past year, McElroy has subscribed to three channels devoted to mystery and real crime shows, as well as a "We Are Darren Wilson" video channel.

McElroy has rarely used her Twitter account, though she did post a message in late-October in response to a news report that several Ferguson drug cases had to be dropped because Darren Wilson failed to show up for court hearings. "drug thug will be arrested again who cares," wrote McElroy.

And her behavior on Facebook indicates a bias toward Wilson's story:

In the weeks after Brown's shooting—but before she contacted police—McElroy used her Facebook account to comment on the case. On August 15, she "liked' a Facebook comment reporting that Johnson had admitted that he and Brown stole cigars before the confrontation with Wilson. On August 17, a Facebook commenter wrote that Johnson and others should be arrested for inciting riots and giving false statements to police in connection with their claims that Brown had his hands up when shot by Wilson. "The report and autopsy are in so YES they were false," McElroy wrote of the "hands-up" claims. This appears to be an odd comment from someone who claims to have been present during the shooting. In response to the posting of a news report about a rally in support of Wilson, McElroy wrote on August 17, "Prayers, support God Bless Officer Wilson."

Multiple attempts by the Smoking Gun to contact McElroy—including her three Facebook pages—were left unanswered.

[Image of McElroy via KMOV // Wilson via St. Louis County]