* Alex Pabon loses case in Court of Appeal
* Judgement says conviction safe, but critical of SFO
* Pabon had argued SFO witness lacked credibility (Adds background, quote, bullet points)
LONDON, March 13 (Reuters) - A U.S. former Barclays trader, who alleged his London trial as a defendant in the Libor rate-rigging scandal was unfair because a key prosecution witness lacked credibility, on Tuesday lost an appeal against his conviction.
Alex Pabon had argued the main banking witness for Britain's Serious Fraud Office (SFO), Saul Haydon Rowe, gave evidence that was incomplete or inaccurate and outside his expertise and could have damaged the trader's credibility.
The Court of Appeal said in its judgment it had concluded that Pabon's conviction was safe. "We dismiss the appeal".
Barclays declined to comment.
Pabon's conviction is part of a global investigation into allegations that banks colluded in setting benchmark rates such as Libor (London interbank offered rate), against which rates on hundreds of trillions of dollars worth of contracts and loans are set across the world.
Around a dozen of the world's largest banks have been fined about $9 billion pounds as part of the investigation and about 30 traders have been charged in the UK and United States.
The Court of Appeal also said there was no room for complacency and the case stood as a "stark reminder of the need for those instructing expert witnesses to satisfy themselves as to the witness' expertise and to engage - difficult though it sometimes may be - an expert of a suitable calibre".
Rowe did not immediately respond to a request for comment.
Pabon and former Barclays traders Peter Johnson, Jonathan Mathew and Jay Merchant in 2016 brought to five the number of bankers convicted in Britain over Libor rigging after Tom Hayes, a former UBS and Citigroup trader, was jailed in 2015.
Hayes, who is serving an 11-year sentence, and Mathew, serving a four-year term, have asked the independent Criminal Cases Review Commission (CCRC) to review their cases. The CCRC examines potential miscarriages of justice. (Reporting by Kirstin Ridley; editing by Simon Jessop and John Stonestreet)