Mary Kate Ordered To Give Evidence on Heath's Death

Mary Kate Olsen (Stephen Lovekin/Getty Images)

Mary Kate Olsen has already been ordered to give evidence in the investigation into Heath Ledger's death, it has been revealed.

So far Mary Kate has refused to talk to cops trying to figure out how the Dark Knight star illegally obtained the prescription drugs that were found in his body.

The Full House star has even tried to cut a deal with the authorities guaranteeing that she won't be charged with any crimes if she talks to them.

But today ABC News revealed that federal officials have already subpoenaed the 22-year-old to appear before a Federal Grand Jury to talk about the case on April 23rd.

The Drug Enforcement Agency has not yet hauled her in to answer questions, and continue to negotiate with her lawyers to find an approach that everyone is happy with.

But as they case drags on, the DEA may demand that she helps them with their inquiries.

When Heath died from an accidental overdose on January 22nd, doctors discovered the powerful painkillers OxyContin and Vicodin in his body -- even though he did not have a prescription for it.

The DEA thinks they may have been acquired with forged prescriptions or from a dealer.

Investigators have already interviewed various people, including Heath's doctors and his ex, Michelle Williams, and say that Mary Kate is the last witness they want to talk to.

Mary Kate has refused two requests to help out with the probe. 

Suspicions about her role in Heath's death were raised because, when Heath's masseuse found his body, she called MK before dialling 911.

Then Mary Kate sent her bodyguard straight 'round to Heath's apartment, and he arrived at the same time as the emergency services.