by Carl Calvert of Calvert Consulting

The obvious place for maps in law is to define boundaries of some sort, property boundaries being the most obvious. Another purpose is to map an alleged route a defendant took or could not have taken in a criminal case. Generally, the overriding purpose is to show, on a piece of paper or computer screen, a representation of the ground to a court.

And the myriad aerial and satellite views of the Earth available on the web? Either these do not show all the detail to sufficient accuracy or the detail required to be seen is in shadow, under the trees or obscured by other detail.

Finally, a map or geographic information system may be the subject of intellectual property rights, such as copyright or database right. Then the matter could be the subject of copyright infringement.

So what use is an expert? A judge told me that she did not need a surveyor to measure the map for her; she could do that herself. What she needed was someone to interpret the map. In other words: what do the lines mean?
Some readers may have seen a Land Registry (LR) Title Plan. That is an Ordnance Survey topographical maps showing ground detail, not legal boundaries. LR uses the ‘general boundary rule’, which in essence states that the legal boundary may be somewhere on or near the physical boundary but does not state exactly where. In some cases (Derbyshire County Council v Fallon [2007] EWHC 1326 (Ch)) the court has held that the pre-registration deed plan was important in deciding where the boundary was. Fortunately, in that case the pre-registration deeds were accurate and had been drawn up as the result of a proper land survey which assisted the court in its determination.

Generally, the rules of copyright require that what has been copied has qualitative and quantitative merit. That can be difficult to prove unless the mechanics and science of mapmaking is understood.

In all things the expert is just a translator with an ability to explain to the court how the lines and colours on the map were determined, their accuracy and what they mean. It has been the case where I have been required to explain a point of law in court, but that was, I believe, unique; and while experts may have a good understanding of law, their function is strictly according to the rules of the court.