It was the middle of the night when the phone call came. 

Gazelle Sharmahd was woken up by her mother, who told her that her father, Jamshid, was calling from his jail cell in Iran. Gazelle hadn't been allowed to talk to her father, an Iranian-German businessman, for two years.

"We didn't even know if he'd already been executed and they hadn't told us," she told me from her home in Los Angeles a few days later.

Iran sentenced Jamshid Sharmahd to death last February for so-called "corruption on Earth" - a vague catch-all term the Iranian regime uses for any expression of opposition. Amnesty International condemned his trial as a sham.

His daughter was overjoyed to talk to her dad again, but she is tormented by the fear that this phone call was allowed in order for her to say goodbye before his execution.

For almost three years the 68-year-old has been in solitary confinement in an Iranian jail, cut off from the world. During the one-hour phone conversation his daughter suddenly realised he hadn't even been told about his death sentence.

Earlier this month Gazelle Sharmahd launched a criminal complaint here in Germany, calling on German state prosecutors to investigate eight high-ranking members of the Iranian judiciary and intelligence service for crimes against humanity, because of the way her father has been treated.

Her father has lost his teeth - either through malnutrition or violence - so he can't eat. He can't walk or talk properly because he suffers from Parkinson's and is not being given his correct medication.

"They're killing him softly in solitary confinement in this death cell. But even if he survives that, they're killing him by hanging him from a crane in public," she said. "They want a public execution for my dad, to send out this message of terror: that anybody who speaks out against the regime, we can do this to you - look at this person that's hanging there."