Heard has taken this step as she believes that Johnny's alleged drug, alcohol and prescription med usage contributed to the abuse alleged by her earlier.

"Johnny's relationship with reality oscillates, depending upon his interaction with alcohol and drugs. As Johnny's paranoia, delusions and aggression increased throughout our relationship, so has my awareness of his continued substance abuse," read the document.

Responding to the IME request put forth by Heard, Johnny's attorney stated that it makes no sense to run a test today at a time when the couple's past is what's in question.

"This is a defamation case in which Mr Depp does not allege that he suffers from any mental disorder or condition. Thus, Mr Depp's mental condition is not 'in controversy' nor does good cause exist under the rule for an IME of Mr Depp," said the lawyer.

Last year, the 'Pirates of the Caribbean' star filed a USD 50 million defamation suit against his ex-wife Heard. The suit came after they parted ways three years ago in May 2016 following Heard's op-ed in Washington Post about her experience as a victim of domestic violence.

While she never put Depp's name in the piece, the actor insisted it was strongly inferred he was the perpetrator.