Two U.S. Supreme Court justices owned stock in tech vendors or other companies that filed briefs in cases under review by the high court in the past year, a watchdog group said last week.

The justices' ownership of stock in three companies that filed amicus, or friend of the court, briefs in Supreme Court cases during the past year represent a "minefield of potential conflicts of interest and ethical problems" that could damage the court's reputation, said Fix the Court, a group advocating for more transparency at the court.

Chief Justice John Roberts owned up to US $750,000 in shares of Time Warner and its subsidiaries at the time the media giant filed a brief in ABC v. Aereo, which broadcasters won 6-3 last June, with Roberts in the majority. Aereo was a start-up offering TV service to subscribers through specialized antenna farms.

Justice Stephen Breyer owned up to $100,000 in IT services firm EMC and Roberts held up to $50,000 in Hewlett-Packard last year when both businesses filed briefs in favor of Teva Pharmaceuticals, which won its patent case against generic drug maker Sandoz, 7-2, with Breyer and Roberts in the majority.

Justice Samuel Alito also held stock in publicly traded companies last year, Fix the Court said. The Supreme Court has nine justices.

The court's media relations team didn't immediately respond to a request for a comment on the Fix the Court report. Fix the Court planned to post the financial reports on its website late Thursday.

The Supreme Court released justices' annual financial disclosure reports Friday. The financial reports are available as paper documents; the court does not post them online.

Fix the Court called on the justices to place their securities into blind trusts, as is done by presidents, presidential candidates and many members of Congress.

"It's impossible to say whether justices' stock ownership played a factor in their decisions, but we shouldn't have to ask that question," Gabe Roth, executive director of Fix the Court, said in a statement.

Fix the Court also called on justices to post their financial disclosure forms online, as is done in Congress and the executive branch of government.

To obtain the financial reports, Fix the Court downloaded and filled out a form from the Administrative Office of U.S. Courts (AO) website and faxed it in. The group received a notice the reports were ready seven weeks later and was charged $.20 a page for the reports.

Staff went in person to present a $17.20 check at the AO building in Washington, D.C., after which AO staff handed over the paper reports.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's email address is grant_gross@idg.com.