[lfowles]

I'm not completely clear on the role of expert witnesses either, I assumed it was someone who was an expert in the field occasionally called to be a witness but their day job is not to be a witness (despite getting paid for it).

[kevin_thibedeau]

There are people who make a career out of being an expert witness. For engineers it requires having a PE certificate at a minimum which is rare in most industries in the US. This allows the professional experts to command high fees.