The old caution against ascribing to malice what can be explained by incompetence is worth keeping in mind when evaluating a high-profile blunder in either the private or public sector, such as the Internal Revenue Service's targeting of conservative groups for extra scrutiny.

But the latest twist in the long-running controversy — the eye-rollingly convenient loss of IRS e-mails — moves the needle from ineptitude and toward the other, more troubling end of the spectrum. While the lost e-mails aren't definitive proof of an orchestrated effort by the IRS or the Obama administration, the recent news that thousands of e-mails were obliterated in a computer hard-drive crash in 2011 is tough to swallow, not only for technology professionals, but also for an increasingly tech-savvy public.

Americans deserve better answers than the current bitterly partisan political process is likely to yield, especially when such a powerful agency has come under suspicion. Congressional Republicans including Minnesota Rep. Erik Paulsen, along with some Democrats, have called for a special prosecutor to investigate how the IRS handled petitions from conservative groups for tax-exempt status.

That's a necessary step, and the request should be expediently heeded by the Obama administration. Although there are two investigations underway in the Republican-controlled House, a nonpartisan review by an investigator with bipartisan respect and technological expertise is sorely needed. The public needs reassurance that the nation's tax-collection agency is run with integrity and that anyone who may have abused its formidable authority has been held accountable.

The decision on whether to appoint a special prosecutor, officially called a special counsel, lies with the Department of Justice. IRS officials have insisted that the lost e-mails were just an unfortunate computer meltdown and that the extra scrutiny of groups with "Tea Party" and "Patriots" in their names was a regrettable mistake. If this is trumped-up, as Democrats often and sometimes accurately deride other House investigations, there's nothing to fear by appointing a special prosecutor to put this long-simmering scandal to bed.

It's foolish to think this is going to blow over — or that it should. A May 2013 report by the Treasury Inspector General for Tax Administration unequivocally concluded that the agency used "inappropriate criteria that identified for review Tea Party and other organizations applying for tax-exempt status based upon their names or policy positions.''

Democrats and IRS officials sometimes portray that report as exonerating the agency because agents gave extra scrutiny to a variety of groups applying for similar status. But a thorough reading of the report underscores that conservative groups were targeted. While applications for other groups were sometimes forwarded for additional review, the Inspector General found that "all cases with Tea Party, Patriots or 9/12 in their names were forwarded" for extra scrutiny during the time investigators sampled.

The process lengthened the time it took for these groups to get through the system and sometimes led to unnecessary or burdensome requests for information, such as the names of donors. The Inspector General also disputed the agency's assertion that its corrective actions were adequate.

The outrage over the missing e-mails is understandable. They belonged to Lois Lerner, a top IRS official. Lerner has refused to testify before Congress, citing her Fifth Amendment rights. What was in her inbox from 2009 to 2011 could have shed light on whether she or higher-ups ordered the extra scrutiny of political groups.

That so many e-mails were unrecoverable after a hard-drive crash is possible, but it strains credulity, according to tech experts contacted by an editorial writer this week. The IRS at the time limited the amount of e-mail storage on its servers, a common practice. Employees were told to archive e-mails on their hard drives.

However, data are often recoverable after a crash, with physical damage to the computer most likely to cause extensive loss. That so little was recoverable suggests that the IRS didn't try very hard to recover Lerner's data.

The IRS expects Americans to hold onto receipts and other documents for years. The agency's lackadaisical data management suggests a higher bar for the public than agency officials. That the IRS dallied in telling Congress about the lost e-mails raises further questions about what happened. Lerner's unwillingness to testify is also troubling. And there's the timing of her hard-drive crash, which came 10 days after a Republican congressman sent a June 3, 2011, letter to the agency inquiring about audits of donors to the type of organization that had come under extra scrutiny.

It was frustrating watching congressional hearings last week. New IRS Commissioner John Koskinen blew off concerns about the missing e-mails. Republicans' understandable frustration yielded little new information. Few if any had the technical expertise needed to really sort out what happened.

A special prosecutor could compel stronger cooperation from the IRS, consult technology experts and bring charges if necessary. Appointing one is a necessary and reasonable step to ensure that the American people learn the truth.

To view a related video report by editorial writers Jill Burcum and John Rash, go to http://tinyurl.com/StribIRS.