Along the lines of when is an expert not an expert, Larry Daniel posts the following quote in his article about using an unqualified person to perform computer forensics,
"Hickory Brands hired a service provider called Computer Ants, whose owner and operator, Thomas Scott, testified to never having performed forensic services in the context of a lawsuit. Scott, who the defendants tasked with producing documents responsive to search terms from a total of 308 million potentially relevant files on 35 computers and six servers, had previously worked as a truck driver and a security manager for Bass Pro Shop."
"The result was the delivery of 1,700 sensitive documents to the opposing counsel that resulted in a heated clawback motion, in which the judge found that the attorneys did not take the "reasonable steps" required by law to prevent the disclosure."
You can read more about that case by clicking here.