LONDON — Britain’s Supreme Court is expected to rule today on whether to approve the extradition of WikiLeaks chief Julian Assange to Sweden, a potential turning point in the Internet activist’s controversial career.

Assange, 40, has spent the better part of two years fighting attempts to send him to the Scandinavian nation, where he is accused of sex crimes. At least one extradition expert said that his long-running legal campaign may finally yield a victory for the Australian programmer.

“When he first started out, I thought: ‘He hasn’t gotten much of a chance,’ but now I’m much more hopeful.” said Karen Todner, whose company, Kaim Todner Solicitors, has fought many high-profile extradition battles. “I would say that in the last few months there has definitely been a swing in favor of defendants in relation to extradition.”

Assange is best known for revealing hundreds of thousands of secret U.S. documents, including a hard-to-watch video that captured U.S. forces gunning down a crowd of Iraqi civilians and journalists that they’d mistaken for insurgents. His release of a quarter-million classified State Department cables outraged Washington and destabilized American diplomacy worldwide.

But his secret-spilling work came under a cloud after two Swedish women accused him of molestation and rape following a visit to the country in mid-2010. Assange denies wrongdoing, saying the sex was consensual, but has refused to go to Sweden, saying he doesn’t believe he’ll get a fair trial there.

Assange’s appeal before the Supreme Court has little to do either with WikiLeaks or with the Swedish sex case itself. His lawyers are seeking to quash his warrant on the ground that it was improperly issued by a prosecutor, not a judge. The Swedish government argues that’s the way the system works in Sweden, as in many other European countries.

In Stockholm, former senior prosecutor Sven-Erik Alhem expressed frustration with the delays, saying that European arrest warrants “should work efficiently and rapidly” and that he was surprised that the legal wrangling in Britain had dragged on for a year and a half.

“If I were in his shoes, I would have been going to Sweden at once to get rid of this horrible situation where an investigation has been going on for so long,” Alhem said.