Donald Trump, a former president of the United States, is facing new legal difficulties as Manhattan district attorney Alvin Bragg prepares to present proof of his involvement in providing hush money to a porn star while campaigning to be president in 2016.

A key witness in the case, David Pecker, former publisher of The National Enquirer, an outlet that oversaw the deal payment with porn star Stormi Daniels, was seen entering the building where the grand jury was convening on Monday, according to the New York Times. 

The Times reported that Mr Bragg has already empanelled a grand jury and is set to begin the presentation of evidence.

Campaign officials from the 2016 Trump presidential campaign have also been contacted by prosecutors who seem determined to reestablish the sequence of events that led to the hush payment back then.  

To learn the facts, subpoenas for the witnesses’ phone records have also been issued.

The jury will hear testimony from Deborah Tarasoff and Jeffrey McConney, both employees of the Trump Organisation, as well as Dylan Howard, a former editor at The National Enquirer.