President Donald Trump’s signature is getting a lot of attention after the House Oversight Committee obtained an infamous 2003 “birthday book” gifted to the late sex offender Jeffrey Epstein that appears to include a signed note from none other than Trump himself.

While people online debate whether Trump is really the author of the birthday note to Epstein, a handwriting analyst told HuffPost what signs to look out for, in general, when analyzing someone’s handwriting for authenticity.

Trump has vehemently denied that he wrote the 2003 letter to Epstein, which features printed text within a hand-drawn outline of a female body and bears Trump’s name and apparent signature.

The president filed a lawsuit against The Wall Street Journal in July after it was the first to report on the birthday note’s existence.

Public interest in the note resurged this week after Democrats on the Oversight Committee released an image of it on Monday.

Following the release of the image, White House press secretary Karoline Leavitt wrote on X: “As I have said all along, it’s very clear President Trump did not draw this picture, and he did not sign it.”

White House deputy chief of staff Taylor Budowich also released a statement on X on Monday claiming that the “Donald” signature at the bottom of the note does not match the president’s signature, leading a lot of people online to examine how Trump has signed his first name in the past.

Trump was once friends with Epstein, a wealthy financier, who died in federal prison one month after being arrested on charges of sex trafficking minors in 2019. His administration continues to face criticism over its refusal to make all the files on Epstein public.

Generally speaking, when evaluating whether a signature is authentic or not, it’s important to note that “it’s impossible to sign your name exactly the same way twice,” said Sheila Lowe, a forensic handwriting examiner and author.

“The first thing is to establish the writer’s personal range of variation, which is a very individual thing — some people have a wide range of variation, some have a very narrow range,” she told HuffPost. “Once that is established, I examine the disputed signature to determine whether it fits within the writer’s range.”

Lowe explained that she does this by looking at a “dozen of factors,” such as spatial arrangement, letter designs and writing movements — which includes features like rhythm, speed and pressure. She noted that pressure can only be determined with an original document, not a copy.

Lowe explained that some people will change their signatures over time for various reasons, and that changes in a signature are an individual thing that’s “impossible to generalize.”

But she said, “bottom line,” once we “settle on our signature, it has a ‘master pattern.’”

“It is extremely difficult to simulate someone else’s master pattern,” she said.

As for how to tell whether a signature has been forged, Lowe said it all depends on the type of forgery, i.e., whether it was traced or simulated. But overall, she said, a forged signature will have a “lack of naturalness.”

“There may be tremor (shakiness), and usually there will be hesitations — stops and starts,” she said.

As it relates to debates surrounding Trump’s signature and the “birthday book,” Lowe said that the president “had a quite different signature when he was much younger, so it is important to compare the disputed signatures to some exemplars that were done within a reasonable time frame.”

“Some of his recent signatures are showing differences from a few years ago,” she added.