Depp is suing Heard for $50m (£38.2m). He alleges that Heard implied that he abused her in a 2018 Washington Post op-ed about domestic violence.
Heard is countersuing for $100m (£80.9m), accusing Depp of orchestrating a “smear campaign” against her and describing his lawsuit as a continuation of “abuse and harassment”.
On Twitter, Riley shared a thread by another user entitled “Johnny Depp: a problematic history”.
The thread details a number of Depp’s past controversies, including his friendship with Marilyn Manson, and the allegations of abuse which are currently being discussed at the defamation trial.
“I wouldn’t wish this guy on my worst enemy,” wrote Riley.
The presenter is one of many celebrities to have voiced their apparent support for Heard, with Julia Fox and Kathy Griffin also among those to speak out.
Others, meanwhile, have publicly thrown their support behind Depp, with celebrities including Winona Ryder, Javier Bardem and Eva Green appearing to take the Pirates of the Caribbean star’s side in the dispute.
You can follow the latest updates from the trial here.