Faegre Baker Daniels partner Mark Voigtmann authored the following article for the Control System Integrators Association in August 2015.
Here is a legal lesson for a rainy day: Responsibility for the defective design of a control system is mostly about drawing lines. Whoever draws the brightest lines wins.
What do I mean? It’s because the design of a system solution, by necessity, often involves multiple “cooks.” It involves the end-user, of course, as well as its constituent stakeholders and an intervening contractor or two. In fact, it can involve multiple disciplines.
Exactly how the design is implemented is beside the point. Whether your company follows the highly structured protocols of ISO 26702 or simply employs a well-worn development process handed down from one generation to the next, the important thing is not the how, but that the opportunities for affecting design are numerous.
This can be a very helpful thing to the integrator. That is because in those unfortunate situations where the broth is sent back to the kitchen, it is rarely only the integrator who cooked it.
But this can also be detrimental. If the end user’s contribution was chiefly to blame for the problems, but the integrator has tinkered with them so much that they are now his own, it can be difficult to redirect the blame elsewhere.
Such blurring of the lines may also waive a very important legal defense. In U.S. courts the longstanding and widely-accepted legal principle called the "Spearin doctrine" (named after one of the parties in a 1918 court case) provides that the end user’s spec, or even its selection of equipment, carries with it the implied warranty that if the spec is followed (or the equipment used), the result will be adequate. In other words, if a reasonable application of the spec does not work, the integrator may not be liable.
That is why in even the most convoluted projects, where multiple contributors are “designing,” it can be important to draw bright lines. Wherever possible, follow a design protocol. Lock down scope. And procure written sign-off at each step.
In a perfect situation — and, yes, I realize most factory floors aren’t that — a bright line between your company’s contribution to system design and the other person’s should be reasonably clear.