Officials in New York and Washington, DC, are preparing for potential protests as a grand jury empaneled as part of the investigation into Donald Trump's alleged role in a scheme to pay hush money to adult film star Stormy Daniels continues to weigh possible charges.

Robert Costello said he told the grand jury Cohen essentially acted alone in paying Stormy Daniels. Cohen disputed the account on MSNBC, saying Costello has his "facts twisted."

The grand jury empaneled as part of the investigation into Donald Trump's alleged role in a scheme to pay hush money to adult film star Stormy Daniels on Monday heard from a potentially key witness put forward by the former president's legal team.

The former president is expected to be indicted soon by a grand jury for his role in a hush money payment made to porn star Stormy Daniels on the eve of the 2016 election.

Lawyer Robert Costello testified at the request of the Trump legal team and said a key prosecution witness is unreliable.

Donald Trump could be indicted​ in New York. Here's how the criminal investigation unfolded, dating back to ​his alleged affair with Stormy Daniels.

The grand jury is considering a case against the former president over hush money paid to ex-porn actress Stormy Daniels. The case may see criminal charges brought against Mr Trump. Mr Costello has been called by Mr Trump's legal team to discredit previous testimony by Mr Cohen.