The author is a civil engineer who has lived and worked in different countries where he has undertaken numerous engineering expert roles. This has included roles concerned with litigations and disputes, forensic investigations of engineering failures and accidents as well as insurance claims advisory roles. Some advice is given about what is expected of an expert witness, and it is intended that this paper will be a useful primer for engineers being engaged as expert witnesses, particularly if that work is in the UK or the USA. © 2017 ICE Publishing. All rights reserved.