Police are investigating whether Dr Scott Lewis was climbing between balconies at the Goldsbrough Mort building in Pyrmont on Saturday morning when he slipped and fell, landing on the balcony of an apartment six floors below. He died at the scene.

Detectives do not believe the circumstances of the 50-year-old's death are suspicious but say they may never know exactly why he plunged to his death.

''There's probably only one person, who's no longer here, who can tell us the story,'' Inspector Glen Jacobs said.

But Mark Kornhauser, who performs a comedy magic act in Las Vegas and has known Lewis for 20 years, said from the US that he believed his friend simply fell over the balcony's railing.

Kornhauser said that Lewis was known for being clumsy

''I know Scott really, really well and I know that he wouldn't have jumped, that he wouldn't have been going from one balcony to another,'' Kornhauser said. ''He was a very timid, cautious person.

''I also know this about Scott, he was a very clumsy guy.

''We lived together for periods. He'd stay at my house when he was working in Vegas. We'd stay up late and I'd see him walk into the kitchen to get some food and he'd be stumbling because he was tired.

''He was notoriously clumsy for spilling drinks at restaurants or dropping things, that kind of stuff.

''He didn't do any drugs, no alcohol. I would go completely with the fact that he was disoriented and he stumbled and fell over.''

Lewis was based in Los Angeles but travelled to Sydney for a show entitled The Illusionists 2.0, which opened at the Sydney Opera House on Thursday.

On Saturday morning, he failed to board the shuttle bus that was to transport him and fellow performers to the venue and his body was found about 9.40am on a fourth-floor balcony at the apartment building in Pyrmont Street, Pyrmont.

Kornhauser said he spoke to Lewis about 24 hours before his death and his friend was anxious about his performance with The Illusionists magic troupe but there was no indication that he was contemplating suicide.

''He was in a high-stakes game with these guys,'' Kornhauser said. ''These are really top-notch guys and they're in their element and, for Scott, he was not in his element.

''He was insecure like all performers are and, in that very competitive environment, he was feeling a lot of stress. But again, he was not ever going to do something like jump off the balcony. He was like every performer and he was dealing with it.''

Kornhauser said Lewis' friends were planning a memorial at the Riviera Hotel and Casino in Las Vegas, where Lewis had performed for nine years.

The Illusionists 2.0 matinee show was cancelled on Saturday. On Saturday night, the audience was not told of Lewis' death until the end of the performance, when the other six cast members were taking their bows.