A: The answer is that you can be both. Here are 2 examples to illustrate:
1. Let's say in June you were hired by a lender. The job was to prepare a refinance appraisal on a single-family property. Your value estimate was $500,000.
Then in August, you get a call from an attorney, telling you that the owners of that single-family property you appraised in June are now getting a divorce. He is calling to give you a heads up and intends to serve you with a subpoena that will require you to produce a copy of your June appraisal. He will also be asking you to testify at a deposition. He will ask you a few questions about your report, but doesn't think it will take much more than an hour. The attorney also tells you that counsel for the wife will also be present at the deposition, and might ask you questions as well. If you cannot appear on the date noted in the subpoena, they would be happy to work with you to reschedule.
In this case, you would be acting as a "fact" witness. You could face questions about your assignment and they may ask you to verify that they have a complete copy of the appraisal from what you prepared in June. The questions are limited to what you did, what you saw, etc.
2. We are still talking about the refi appraisal you did in June. This time you get a call from counsel for the husband/property owner, still in the midst of a divorce. Counsel knows you appraised the home in June, so you are familiar with the property. He also thinks your value estimate was accurate.
He tells you that counsel for the wife has an appraisal that says the current value of the subject is only $300,000. Counsel for the husband would like to retain you to ask as an "expert". He wants to speak to you about the June report you did for the lender. He would also like you to prepare a current appraisal, so that you can confirm that the condition of the home is unchanged, since June. Lastly, he would like you to look at the appraisal prepared for the wife and get your feedback on that report, on the comps that were selected, etc.
For No. 2, you could be acting as both a "fact" witness and as an "expert" witness. When questioned about your refi appraisal, or any current appraisal you prepare, you will be asked to speak about things that are within your personal knowledge...what you did, what you saw, who you spoke to, etc.
If you accept the assignment to look at the other appraisal report, you are now offering your opinions. Do you think the comps in that report are truly "comparable" to the subject? Do you agree with the other appraiser's adjustments? The other appraiser claims the subject is on a busy street, and he adjusted downward for that; do you agree?
This is one example of a situation where you could be acting as both a "fact" witness (answering questions about your personal knowledge) and as an "expert" witness (providing your opinions based upon your professional knowledge and experience.