Three weeks after the trial phase ended in the US government's suit to block Oracle from buying PeopleSoft, the judge presiding over the case continues to grill both sides as to why documents and testimony filed under seal should be kept confidential.

Judge Vaughn Walker apparently wants the explanation behind his decision, which is due to be issued in the coming weeks, to be as open as possible and not constrained by having to avoid discussion of materials filed under seal, one legal expert said.

"The Oracle case is a high-profile case, and his decision will be analysed and the subject of considerable comment," noted Jeff Shohet, a San Diego-based partner with Gray Cary Ware & Freidenrich, which is not involved in the case.

The Department of Justice filed suit in February to block Oracle's hostile takeover attempt, arguing that the deal would stifle competition and lead to higher prices. Oracle responded that Germany's SAP, along with dozens of smaller rivals, would provide it with plenty of competition.

The two-month trial ended 20 July with closing arguments in federal court in San Francisco. There was no jury and Judge Walker is expected to issue his decision this month or next. The merger also needs approval from European regulators and PeopleSoft's shareholders.

Judge Walker expressed frustration throughout the trial at the amount of material filed under seal. It includes documents and testimony describing the competitive strategies of Oracle, PeopleSoft and other vendors, the mechanics of complex software deals and the ins and outs of vendor discounts.

Last week, he ordered all parties in the case to show cause why the materials submitted under seal should not be made public. Oracle and the third parties, including Microsoft, SAP and several large customers, filed their arguments this week, spokespeople for Oracle and the DOJ said. A hearing on the matter is set for the end of next week.

With the case being so closely watched, Judge Walker will be looking to write a clear and complete decision that can be scrutinised publicly, without having to dance around sealed material or issue a heavily edited, or "redacted", document that may be harder to comprehend, Shohet said.

"Judges are under considerable pressure from news services and others to maintain public access to judicial proceedings. Judge Walker writes thorough opinions in high-profile cases ... and he does not want to be constrained in explaining his reasoning," he said.