AP- In a shift that could significantly hurt Olympic champion Marion Jones and other athletes under investigation for possible drug violations, the U.S. Anti-Doping Agency plans to start using a less-stringent burden of proof in doping cases.

The Associated Press obtained a copy of a USADA memorandum calling for such a change, which was dated June 1 and written by USADA Director of Legal Affairs Travis Tygart. The existence of the memo was first reported Sunday by The Washington Post.

USADA spokesman Rich Wanninger said Sunday he could not comment.

The memo says the standard burden of proof used in U.S. criminal courts – “beyond a reasonable doubt” – has been replaced with the requirement that USADA prove doping “to the comfortable satisfaction” of the panel hearing the case.

Tygart’s memo said the change reflects world anti-doping rules that took effect March 1.

Such a change could make it much easier for the USADA to conclude there were doping violations that could lead to bans from this summer’s Athens Olympics.

Jones won an unprecedented five track medals at the 2000 Sydney Olympics and has hinted she might try to match that mark at the Athens Games. She repeatedly has denied using performance-enhancing drugs and has vowed to fight any USADA charges.

Jones met with USADA officials last month to discuss possible drug evidence against her, and received a letter from the agency this week asking follow-up questions. On Friday, she asked that her grand jury testimony in the Bay Area Laboratory Co-Operative steroid distribution case be released to her so she could pass it on to the USADA.

She was one of several dozen athletes who testified last fall before a grand jury that ultimately indicted four men on charges of distributing steroids to top athletes.

Four prospective Olympic medalists – including Jones’ boyfriend, 100-meter world record holder Tim Montgomery – received letters last week informing them the USADA is pursuing possible doping cases against them that could result in bans from the Athens Games.

The USADA probe of Jones and other athletes is based on documents from the grand jury investigation of BALCO that were subpoenaed by a Senate committee and then turned over to the USADA. None of the athletes has failed a drug test.