Though Dunaway announced that "La La Land" won the night's biggest honor, the statuette actually went to "Moonlight."
For the past 83 years, PricewaterhouseCoopers has been responsible for tallying the votes. Like years before, partners Martha Ruiz and Brian Cullinan headed up the operation.
The two opened up to ABC News in 2016 about how the process works, which could give some insight into what went wrong Sunday.
1. Voting started early: After the nominations are announced, ballots are sent out to members of the Academy, each of whom decided ahead of time whether to vote electronically or with a paper ballot. Immediately afterward, according to Ruiz, a small group of PricewaterhouseCoopers employees counts each vote by hand at a secret location.
2. The voting process is an organized one: Though electronic voting was introduced five years ago, many members still choose to use paper ballots.
"We then have those in an undisclosed location. We don’t tell people where the voting takes place or where the tabulation takes place. And we have a team that helps us go through this, but each of our team members are only doing a portion of the total counting and myself and my fellow partner Martha are the only two who really know the winners."
3. There's protection from counterfeit ballots: PricewaterhouseCoopers makes sure that each ballot returned to them is legitimate by matching the code on it to the corresponding voting member. And while Cullinan said at the time that he'd never seen a fake ballot mailed in, he assured ABC News that it would be caught very quickly and wouldn't be counted.
4. Counting the votes takes days: For days before 2016's show, Cullinan and Ruiz holed up with their team counting ballots -- and that process continued for the rest of the week.
"We have a safe. We have multiple rooms with security and biometric locks and all kinds of things. Alarms that if doors are open for too long the LAPD shows up. A lot of those security measures that we have in place just to make sure that’s its always safe," Cullinan said. Ruiz added that once the ballots are counted, they're filed away for a few years and then shredded.
5. Counting the best picture race is complicated: The process of counting votes for best picture isn't as simple as one might think. According to Cullinan, each voter is asked to rank the nominated films, with one being their top choice. After determining which film garnered the least number of votes, PwC employees take that title out of contention and look to see which movie each of those voters selected as their second favorite. That redistribution process continues until there are only two films remaining. The one with the biggest pile wins. "It doesn’t necessarily mean that who has the most number one votes from the beginning is ensured they win," he added. "It’s not necessarily the case, because going through this process of preferential voting, it could be that the one who started in the lead, doesn’t finish in the lead."
6. Each winner's name is printed out to ensure security: Marc Friedland, creative director of Marc Friedland Couture Communications, has been handcrafting the Oscar envelopes and winners cards for six years, though he did not do them for the 2017 telecast. He said in 2016 that the process took 110 hours, as he created three sets of winners cards -- one for each nominee -- and 72 envelopes. When he was finished, he gave the winners cards and the envelopes to Ruiz and Cullinan, who were responsible for putting the correct winners cards into the envelopes and sealing them. Then, they loaded them into briefcases and destroyed the cards bearing the names of those who did not win. Winners also receive a copy of the envelope and the card bearing his/her name. "This is not something that's gonna get thrown aside," Friedland said of his envelope and card. "This is coveted."
7. Security precautions are taken until the end: Ruiz and Cullinan each take a briefcase filled with winners' envelopes to the ceremony, but to ensure maximum security, each travels on a different route and is protected by police. "No matter what happens, at least one of us will get there," Cullinan said. Once they're at the Dolby, the briefcase stays in their hands. "We stand backstage and we hand the envelope to the presenters just before they walk on stage," he added. "It doesn’t really leave my side and I have my LAPD escort with me backstage."