The FBI searched for, but was unable to find any fingerprints on the duct tape.
As I read it...they tested for LA, GA, and LE...none of "theirs" were found...there were "no other LATENT" prints found.....first...there's no info given about IF Casey's prints of any kind were found....AND, no mention IF any "Patent" prints....
[edit] Fingerprint types
[edit] Latent prints
Although the word latent means hidden or invisible, in modern usage for forensic science the term latent prints means any chance of accidental impression left by friction ridge skin on a surface, regardless of whether it is visible or invisible at the time of deposition. Electronic, chemical and physical processing techniques permit visualization of invisible latent print residue whether they are from natural secretions of the eccrine glands present on friction ridge skin (which produce palmar sweat, consisting primarily of water with various salts and organic compounds in solution), or whether the impression is in a contaminant such as motor oil, blood, paint, ink, etc.
Latent prints may exhibit only a small portion of the surface of the finger and may be smudged, distorted, overlapping, or any combination, depending on how they were deposited. For these reasons, latent prints are an “inevitable source of error in making comparisons,” as they generally “contain less clarity, less content, and less undistorted information than a fingerprint taken under controlled conditions, and much, much less detail compared to the actual patterns of ridges and grooves of a finger.”[5]
[edit] Patent prints
These are friction ridge impressions of unknown origins which are obvious to the human eye and are caused by a transfer of foreign material on the finger, onto a surface. Because they are already visible they need no enhancement, and are generally photographed instead of being lifted in the same manner as latent prints.[citation needed] Finger deposits can include materials such as ink, dirt, or blood onto a surface.
ETA: I can TRY to make up possibilities, can't I???