Pattern: Unintended Consequences
[Adapted from Patterns in IT Litigation: Systems Failure (1976-2000)]
Summary: The manufacturer makes some change in the functionality or configuration of the system, which is already in use. The change results in unpleasant or unintended consequences for one or more clients.
Causes: Someone at the vendor/manufacturer mandates or proposes a change, and it gets made without careful consideration of its impact on existing systems or proper testing. The resulting consequences for one or more clients lead to legal action. Note that the only class-action lawsuits represented in our survey all fall into this category and all involve commercial products or services.
Recommendations: Think carefully about the consequence of changes. Test modified products thoroughly. Roll them out in limited numbers with trusted, friendly clients to flush out problems. Act quickly to fix problems that show up.
About the Author: bfwebster
Webster is Principal and Founder at at Bruce F. Webster & Associates, as well as an Adjunct Professor for the BYU Computer Science Department. He works with organizations to help them with troubled or failed information technology (IT) projects. He has also worked in several dozen legal cases as a consultant and as a testifying expert, both in the United States and Japan. He can be reached at 303.502.4141 or at bwebster@bfwa.com. 
![The Meltdown/Spectre CPU bugs: a dramatic global case of the “Unintended Consequences” pattern [UPDATED 4/4/18]](http://bfwa.com/wp-content/uploads/2018/01/intel-cpu-150x150.jpg "The Meltdown/Spectre CPU bugs: a dramatic global case of the “Unintended Consequences” pattern [UPDATED 4/4/18]")