American Science & Engineering Inc v Rapiscan Systems Ltd

In assessing obviousness, the court must consider the differences between the prior art and the claimed invention without knowledge of the invention and without hindsight. A technically simple modification is not necessarily obvious where the prior art gives no motivation for making it and points away from the proposed change. The court must assess the claimed combination as a whole, rather than selecting an isolated feature from one system and combining it with another. Secondary evidence may provide modest support for non-obviousness. Where a party relies on an asserted fact to explain why an invention was not made earlier, that party bears the burden of proving the fact and its relevance.

The claimant was the proprietor of a patent for a mobile X-ray backscatter inspection system. The defendant admitted acts which would infringe if the patent were valid, but counterclaimed for revocation on the ground that the claims were obvious in light of Swift, a 1996 paper describing a mobile X-ray backscatter imaging system.

The principal issues were whether Swift disclosed or made obvious the requirement that the detectors be entirely enclosed within the vehicle during inspection, whether it made obvious a relative motion sensor, and whether the combination of those features was obvious. The validity of subsidiary claims was also considered contingently.

1. Claims 1 and 16. The inventive concept of claim 1 comprised a vehicle containing a flying-spot X-ray source and backscatter detector, with both entirely enclosed in the vehicle during motion and a relative-motion sensor generating a signal enabling correction of image aspect ratio. Claim 16 stood or fell with claim 1.

2. Feature (f). The requirement that the detector module be contained entirely within the enclosed conveyance included concealment from view. Swift did not disclose that feature because its detector doors were opened during scanning. Redesigning the system to operate with the doors shut would require more than a simple change, since the doors would attenuate the signal and might need replacement with non-attenuating material. There was no sufficient motivation in Swift to make that change.

3. Feature (g). Swift did not require a relative-motion sensor because it operated at fixed speeds. Although Mobile VACIS provided relevant common general knowledge, it did not make it obvious to convert Swift into a drive-past system. That conclusion depended on hindsight, particularly because Swift contained no suggestion of drive-past operation and taught away from covert scanning.

4. Combination. Even if the individual steps had been obvious, the combination was not. The skilled person would have had to conceive a mobile, covert, backscatter-only system operating in drive-past mode with a relative-motion sensor. Swift contained no hint of that change and taught away from both covert and drive-past operation.

5. Secondary evidence and burden. The absence of the invention during the six years after Swift and the defendant’s commercial reaction provided modest support for non-obviousness. A party relying on an alleged earlier patent, regulatory restriction or commercial factor to explain the absence of an invention bears the burden of proving its existence and relevance.

6. Subsidiary claims. The question whether claims 7, 11 and 18 were independently valid was academic. Had claim 1 been obvious, none of those claims would independently have been valid.

7. Disposition. None of the claims was obvious over Swift. The defendant’s counterclaim for revocation was dismissed.