(CNN) Former Vice President Joe Biden on Friday denied a former aide's claim that he sexually assaulted her 27 years ago, saying in his first public statement on the matter that the alleged incident "never happened."
His response came as pressure built on the presumptive Democratic nominee to personally address the allegation from Tara Reade, who worked as a junior staffer in Senate Biden's office in 1993 and claims Biden assaulted her that year.
"While the details of these allegations of sexual harassment and sexual assault are complicated, two things are not complicated. One is that women deserve to be treated with dignity and respect, and when they step forward they should be heard, not silenced. The second is that their stories should be subject to appropriate inquiry and scrutiny," Biden said in the statement.
He continued, "Responsible news organizations should examine and evaluate the full and growing record of inconsistencies in her story, which has changed repeatedly in both small and big ways."
CNN has spoken with Reade, her former neighbor, a friend of hers at the time, and her brother regarding the allegation. CNN has also spoken with Biden's campaign and several longtime aides and former staffers to Biden.
Here's what we know about the allegation:
Reade publicly accused Biden last year of touching her shoulders and neck and making her feel uncomfortable. At the time, she did not accuse him of sexual assault.
She first came forward with her sexual assault allegation against Biden in interviews in recent weeks with multiple media outlets, including CNN.
Reade told CNN that in 1993, when she was working as an aide in Biden's Senate office, she was asked to deliver a duffel bag to the then-Delaware senator. In a corridor somewhere in the Capitol Hill complex, Reade said Biden "had me up against the wall; he used his knee to spread open my legs," and "put his fingers inside me."
Reade said when she pulled away, Biden said to her, "Come on man. I heard -- I thought you liked me." Biden then looked angry, according to Reade, and said, "You are nothing to me. You are nothing." She said that Biden eventually took her by the shoulders and said words to the effect of, "You're OK. You're fine," before walking away.
Reade has said that she complained to multiple colleagues in the office about interactions with Biden that made her uncomfortable, but not about the alleged assault. Reade has also said that she filed a complaint with a personnel office on Capitol Hill at the time, but that she does not have a copy of it. It is unclear what kind of complaint -- and with what office -- Reade may have filed. She has said she filed a complaint related to the uncomfortable interactions in the office, but not sexual assault.
Reade said on the night of the alleged assault she spoke on the phone with her mother, Jeanette Altimus, who was "adamant" that she call the police. She said she did not call the police. Reade said she recalls her mother telling her sometime after the alleged assault that she had called into Larry King's show. Altimus died a few years ago.
A newly surfaced video from 1993 appears to feature the mother of Reade calling into Larry King around the time of the alleged assault to seek advice about "problems" her daughter had been having while working for a "prominent senator."
In a "Larry King Live" segment that aired on August 11, 1993, on CNN, an unnamed woman calls in to the show with her location identified on the screen as San Luis Obispo, California. The show was about the cutthroat nature of Washington, DC, politics and media. The woman does not mention sexual assault or harassment, nor does she describe in any detail what "problems" she might be referring to. Her daughter's name and Biden are also not mentioned.
In a phone interview with CNN, Reade said she is certain the voice in the video belongs to her mother.
Lynda LaCasse told CNN in a phone interview that Reade, her former neighbor, told her about the alleged sexual assault within a few years of the incident.
LaCasse said it was 1995, perhaps even early 1996, based on her recollection. LaCasse said she often sat outside on her stoop smoking Virginia Slims, and that on this particular day, she cried as she discussed with Reade a custody battle for her kids. Reade began to cry too, LaCasse said.
"She started talking about Joe Biden. And I didn't really know much about Joe Biden," she said. LaCasse said that Reade told her that when she was working in Washington some years prior, Biden "had pushed her up against a wall and he put his hand up her skirt and he put his fingers inside of her, and she was dealing with the aftermath of that."
CNN verified through public records searches, photos and an examination of Reade's past government identification that LaCasse and Reade were once neighbors.
A friend of Reade's, who asked to remain anonymous in order to protect her privacy, told CNN that Reade told her on multiple occasions while she was working in Biden's Senate office about physical interactions with the then-senator that had made her feel uncomfortable.
The friend told CNN that she and Reade became close in the early 1990s when she spent multiple semesters interning in Washington, DC, to receive college credits. One of her internships was with the late-Sen. Ted Kennedy.
In 1993, when the friend was back in school, she received a phone call from Reade. Reade told her in detail that she had been sexually assaulted by Biden on Capitol Hill. The friend said she believes Reade called her within days of the alleged assault. The friend said she advised Reade against filing a police report at the time.
The Washington Post interviewed Reade's brother, Collin Moulton, who told the paper that she had told him in 1993 that Biden had behaved inappropriately by touching her neck and shoulders but not about the alleged sexual assault. Several days after that interview with Reade's brother, the Post said, "he said in a text message that he recalled her telling him that Biden had put his hand 'under her clothes.'"
Moulton later told CNN that Reade told him in the early 1990s that she had been asked to bring Biden his gym bag, and that in a private setting, he had cornered her against the wall and put his hands under her clothes.
Before Biden denied the allegation himself in a statement and on camera, Biden's deputy campaign manager and communications director, Kate Bedingfield, issued a statement calling Reade's allegation "untrue."
"Vice President Biden has dedicated his public life to changing the culture and the laws around violence against women. He authored and fought for the passage and reauthorization of the landmark Violence Against Women Act. He firmly believes that women have a right to be heard - and heard respectfully," Bedingfield said. "Such claims should also be diligently reviewed by an independent press. What is clear about this claim: it is untrue. This absolutely did not happen."
Marianne Baker, who was Biden's executive assistant in the 1980s and 1990s when Biden was a senator, also previously said in a statement provided through the Biden campaign that she was never aware of any reports of inappropriate conduct, including from Reade.
"In all my years working for Senator Biden, I never once witnessed, or heard of, or received, any reports of inappropriate conduct, period -- not from Ms. Reade, not from anyone. I have absolutely no knowledge or memory of Ms. Reade's accounting of events, which would have left a searing impression on me as a woman professional, and as a manager," Baker said. "These clearly false allegations are in complete contradiction to both the inner workings of our Senate office and to the man I know and worked so closely with for almost two decades."
Ted Kaufman, who was chief of staff at Biden's Senate office when Reade worked there, told CNN that he did not remember Reade and that no complaint about sexual harassment was ever brought to his attention in all the years that he has worked with Biden.
"She did not come to me. I would have remembered her if she had, and I do not remember her," Kaufman said. "I would surely remember because nothing like that ever happened in the 50 years I've been associated with the senator."
Dennis Toner, who was Biden's deputy chief of staff at the time and one of the people Reade said she had discussed her complaints with, told CNN in an interview on Thursday that he had no recollection of Reade or any conversation related to sexual harassment allegations.
"I clearly would remember if we -- that is, if Tara and myself -- had any kind of conversation regarding sexual harassment allegations, let alone something involving Sen. Biden. It would stick in my mind. It would be burned in my mind," Toner said. "I don't understand it."
CNN has interviewed half a dozen former Biden aides who worked in his Senate office in the early 1990s. All of them said they were not aware of any sexual harassment or assault allegations.
The man who led the vetting of Biden as Barack Obama's possible running mate in 2008 said his team did not find evidence of sexual harassment complaints or allegations during Biden's vetting process.
Attorney William Jeffress told CNN's Arlette Saenz that his team of nearly 10 lawyers spent roughly two months "doing every deep dive into his long record in public service," including examining records and interviewing dozens of former and present staffers to the then-Senator. Jeffress said they specifically looked for and asked if anyone was aware of complaints or allegations, including ones pertaining to sexual harassment, made against Biden.
"We asked everybody an open-ended question -- 'Are you aware of any complaints of any illegal, unethical conduct, including discrimination or harassment?' And the answer was uniformly no," Jeffress said. "We never heard of any allegation against him of that sort."
Jeffress said Reade's name did not come up in their vetting process, and no one suggested they speak to her.
Patti Solis Doyle, who served as chief of staff for vice presidential operations during the 2008 election, echoed Jeffress' comments. During a Saturday appearance on CNN, Solis Doyle told Michael Smerconish that "the selection committee had done a thorough vet of all vice president contenders."
"If anything like a sexual assault or a sexual allegation had come up, certainly, I would have been given the heads-up on it. And nothing like that ever came up," she said.
This story has been updated to include comment from two people involved in the 2008 vice presidential selection process or management, as well as Biden's chief of staff at the time of the allegation.