By David Schepp BBC News Online's North America business reporter

For many the guilty verdict reached in the obstruction of justice case against Arthur Andersen signals the end to the already mortally wounded accountancy firm.

The firm's demise was all but guaranteed in March when the US Government indicted Andersen on charges of obstruction of justice for destroying key documents of its audit client, Enron.

Defence lawyer Hardin plans to appeal

Chicago-based Andersen watched as its client base dwindled as company after company began looking elsewhere for another auditor to sign off on their books.

Having been found guilty, the firm now faces a $500,000 fine, among other penalties from the court. It will not know the exact punishment until the 11 October sentencing date.

No one, however, is expected to go to prison, including David Duncan, who oversaw the shredding of documents at Enron and became a government witness in exchange for a reduced sentence.

Improper conduct

But Andersen's fate does not lie so much in the hands of the court but in those of the Securities and Exchange Commission (SEC), which polices American business.

Judge Harmon postponed her holiday for the trial

Given Saturday's conviction, reached after 10 gruelling days of deliberations by the jury, the SEC will probably prohibit Andersen from further practising before it - a penalty far stiffer than a fine.

It was the prosecution's contention from the beginning that those high stakes were exactly the reason Andersen acted in destroying Enron documents, having already incurred penalties for past wrongdoings.

Last year, the firm was hit with a $7m (�4.7m) fine for "improper professional conduct", the first successful case against an auditor launched by the SEC in more than 20 years.

The fine related to auditing work for waste-disposal firm Waste Management in the mid-1990s, including some $1.4bn in overstated earnings.

Wider questions

The Waste Management case followed Andersen's decision to pay $110m to settle a lawsuit on audits at Sunbeam, another US client found to have less than reliable accounts.

The trial also raised questions about the culture of the company.

Andersen accountants working on Enron's books closely identified themselves with the flawed client.

For example, they over-ruled the advice of in-house advisers on ethics, deciding instead to do what Enron wanted.

It raises a wider question about accounting in the US and how it might restore its reputation as the guarantor of the honest presentation of accounts.

Hurtful changes

Former Federal Reserve Chairman Paul Volcker hoped to correct that perception by overseeing changes at Andersen when appointed to an oversight role in February.

But by the time the case was under way in Houston, Mr Volcker's efforts were all-for-nothing as Andersen began parcelling itself off to willing buyers while its units were still appealing.

There was no longer an Andersen for Mr Volcker to reform.

Now, there is concern around the world because stock markets are plummeting when an improving economy indicates that they should be rising.

The disparity is blamed on mistrust of company accounts.

Big accounting firms are mounting a substantial, expensive lobbying operation in Washington to avoid what to them could be hurtful changes being proposed by Congress.

But if there is a lesson to be learned from the Andersen case, it is that accountancies are slow to reform.

It may take many more Enron-like cases to emerge before any real change is implemented.