Ex trader Hayes wanted to do job perfectly, Libor trial hears

* Defence opens case in trial of alleged Libor manipulator

* Defendant Hayes, former UBS (NYSEArca: FBGX - news) , Citigroup (NYSE: C - news) trader, takes stand

* Hayes denies dishonesty, says wanted to do job well

By Kirstin Ridley

LONDON, July 7 (Reuters) - Tom Hayes, the first person to face trial by jury over allegations he conspired to rig global Libor interest rates, told a London court on Tuesday he had not acted dishonestly and just wanted to do a good job.

Taking the stand for the first time in the high-profile trial at Southwark Crown Court, the 35-year-old former UBS and Citigroup star trader said he had only admitted to wrongdoing in interviews with British officials because he wanted to avoid extradition to the United States.

"Basically, I was petrified," the Briton said, adding he feared facing charges in the United States that might carry jail sentences of 20-30 years.

By admitting to wrongdoing, Hayes said he believed he was ensuring his case would be heard in Britain. But he added he did not think he had acted dishonestly, and that he had simply wanted to do a good job for his employers.

"I wanted to do my job as perfectly as I could," he said.

Hayes, a former yen derivatives trader based in Tokyo, has pleaded not guilty to eight counts of conspiracy to defraud between 2006 and 2010 -- an offence that can carry a 10-year jail sentence.

Britain's Serious Fraud Office (SFO) alleges Hayes set up a network of brokers and traders that spanned some of the world's most powerful financial institutions to influence Libor rates -- designed to reflect the cost of inter-bank borrowing -- for his own trading benefit, prejudicing the interests of others.

According to the transcripts of Hayes's interviews with the SFO after his arrest in December 2012, Hayes said he was extremely open about trying to influence rates, his managers knew what he was doing and that the practice was widespread.

Based in Tokyo, Hayes traded in yen-denominated derivatives tied to Libor -- the London interbank offered rate that determines the prices of around $450 trillion of financial contracts and loans worldwide. Small movements in the rate could translate into big profits or losses for his trading book.

Hayes was diagnosed in May by an independent medical expert with mild Asperger's Syndrome -- a form of autism -- and has been allowed to sit with his legal team and an independent intermediary while the prosecution laid out its case. The glass-enclosed security dock, where defendants more usually sit, has instead been used by journalists as it affords a better view of proceedings than the public gallery.

Judge Jeremy Cooke started the day by telling the jury that people with Hayes' condition often did not detect shades of grey but tended to see the world in black and white. (Reporting by Kirstin Ridley; Writing by Mark Potter; Editing by Keith Weir)