A Canadian prosecutor said Charles Ng, wanted in California for allegedly carrying out a string of murders, joined forces with a mass murderer in the early 1980s to kidnap targets for sex slayings. As Ng’s extradition hearing began in Edmonton, Alberta, amid tight security, Federal Crown Prosecutor Bruce McFarlane told a packed courtroom that he will argue that Ng and his companion, Leonard Lake, “were acting in concert to achieve the same overall objectives.” Ng, 27, has been serving a 4 1/2-year sentence in Canada since his conviction in December, 1985, of armed robbery during a botched shoplifting attempt in Calgary. He came to Canada after Lake committed suicide. That investigation led to the charges against Ng. Lake later was linked to the death or disappearance of 22 people. Canada has a policy of not extraditing criminals who could face the death penalty and is entitled to ask for leniency under the 1986 Canada-U.S. extradition treaty.