Why were engineers negligent in the 1981 Hyatt Regency walkway collapse?

I remember watching a long video about this in my senior seminar course. Scared the hell out of me.

The Wex Law dictionary defines negligence as:

A failure to behave with the level of care that someone of ordinary prudence would have exercised under the same circumstances. The behavior usually consists of actions, but can also consist of omissions when there is some duty to act (e.g., a duty to help victims of one's previous conduct).

Notice that negligence includes "omissions when there is some duty to act". The key thing to understand is, as the engineer on the project (i.e. the "engineer of record"), it was Gillum's duty to act in a way consistent with the standard of care required of them in their role as an engineer, and they failed to do so.

The bottom line is NOT whose drawing it was originally, or who came up with the design. Not only that (this might be controversial) but it may not have even legally mattered whether Gillum actually stamped the drawings with the design change (though the fact that they did stamp the drawings made the case against them a slam dunk). The stamp signifies something more fundamental: an attestation they were aware and cognizant of the design change.

As the engineer of record on the project, it was the responsibility of Gillum & Associates - legally, professionally, ethically, and practically - to check those drawings, and to make it known that there was a problem on the project if one were found. But even if an engineer is not the engineer of record, if they make a statement in a professional capacity that a design is acceptable without having actually looked at the change, that is negligence.

Some alternate scenarios:

• If Havens Steel and the contractor had made and implemented the change without Gillum knowing, there would have been no negligence on the part of Gillum.
• If Gillum had reviewed the drawing and sufficiently communicated to the manufacturer or the contractor that there was a problem, and yet the modified design was used anyway, it would have been a completely different case and although they would have certainly been part of the litigation, Gillum probably would have survived the storm.
• If Gillum had managed their liability more effectively by explicitly stating in the contract that checking change orders was outside of their scope for the project, then it's possible that they might have escaped the episode since at that point the owner/contractor would have been deviating from the original design without approval. But even in that case, negligently stamping the design change would have doomed them.