Ars Technica:

The government can prosecute and imprison people for crimes based on evidence obtained from their computers—even evidence retained for years that was outside the scope of an original probable-cause search warrant, a US federal appeals court has said in a 100-page opinion paired with a blistering dissent.

The 2nd US Circuit Court of Appeals ruled that there was no constitutional violation because the authorities acted in good faith when they initially obtained a search warrant, held on to the files for years, and built a case unrelated to the original search.

The case posed a vexing question—how long may the authorities keep somebody's computer files that were obtained during a search but were not germane to that search? The convicted accountant said that only the computer files pertaining to his client—who was being investigated as part of an Army overbilling scandal—should have been retained by the government during a 2003 search. All of his personal files, which eventually led to his own tax-evasion conviction, should have been purged, he argued.

But the appeals court said the authorities' behavior was acceptable and didn't reach the constitutional question of whether the Fourth Amendment rights were breached for accountant Stavros Ganias, who was sentenced to two years in prison. That's because three years after the original search of the accountant's files in connection to the Army scandal, Connecticut authorities got another search warrant for Ganias' own tax files that were already in the government's possession, the appeals court ruled in a 12-1 decision Friday written by Judges Debra Ann Livingston and Gerard Lynch. Ganias had subsequently deleted those files from his hard drives after the government had imaged them, according to court records:

Defendant-Appellant Stavros Ganias appeals from a judgment of the United States District Court for the District of Connecticut (Thompson, J.) convicting him, after a jury trial, of two counts of tax evasion in violation of 26 U.S.C. § 7201. He challenges his conviction on the ground that the Government violated his Fourth Amendment rights when, after lawfully copying three of his hard drives for off-site review pursuant to a 2003 search warrant, it retained these full forensic copies (or “mirrors”), which included data both responsive and non-responsive to the 2003 warrant, while its investigation continued, and ultimately searched the non-responsive data pursuant to a second warrant in 2006. Ganias contends that the Government had successfully sorted the data on the mirrors responsive to the 2003 warrant from the non-responsive data by January 2005, and that the retention of the mirrors thereafter (and, by extension, the 2006 search, which would not have been possible but for that retention) violated the Fourth Amendment. He argues that evidence obtained in executing the 2006 search warrant should therefore have been suppressed.

We conclude that the Government relied in good faith on the 2006 warrant, and that this reliance was objectively reasonable. Accordingly, we need not decide whether retention of the forensic mirrors violated the Fourth Amendment, and we AFFIRM the judgment of the district court.

[...]

The bolded part - the 2nd search warrant - is probably at the heart of the issue. Why was it issued? Was the Army overbilling case over, or was the investigation continuing? Why was the data still around?

I don't have time to look through the arguments now, but it's interesting. It would seem to make sense that the rules about how long data is retained, and what should be done with data that is not part of the original warrant, should be looked at.

Cheers,
Scott.

I need to read the decision and dissent, but 12:1 isn't just some lone yahoo in Alabama coming up with novel rationale to put a boot on our necks, I don't think.

Cheers,
Scott.