US v. Harris: Harris was arrested after threatening a woman with a gun. The serial number of said firearm was described as having been "altered" with "numerous deep gouges and scratches across" it. "However," the police report continued, "the numbers are still legible." Harris pleaded guilty to being a felon in possession of a firearm. At sentencing, the district court imposed a 4-level Guideline enhancement for possession of a firearm with an "altered or obliterated serial number," concluding (after an examination of the gun itself) that the damage was not accidental and interfered with the ability to read the number, even if it could be done. Harris was sentenced to 105 months in prison.
On appeal, Harris argued that the district court erred by imposing the enhancement when the serial number was still legible. The Fourth Circuit disagreed and affirmed the sentence. The court noted that Harris's argument, that "altered" means changed so as to make the number illegible was "rational," it didn't take into account the fact that something can be altered if it is less legible than intended, rather than completely illegible. Serial numbers altered in such a way interfere with the regulatory scheme (and the purpose therefore) requiring serial numbers in the first place.
NOTE: This case was decided on June 26, 2013.