We are preparing for a trial where an investigator used GPS coordinates to determine an address location and distance from a cell phone tower. Since he used GPS coordinates would we necessarily have to have an expert to explain how GPS coordinates are determined and if so, does anyone have any idea who may use?

I have a case with the same infomation. I think I'll have to call someone from the cell phone company to testify. If anyone has presented this kind of testimony before, I'd be interested in talking to you about how you did it.

We have a case with same regarding GPS coordinates and we are asking the judge to take judicial notice relying on Jackson v. State, No. 11-08-00011-CR, 2009 TEx. App. LEXIS 5997 (Eastland -- July 30, 2009) where the appellate court took judicial notice of the distance. We are asking the trial court to take judicial notice and give the jury the judicial notice instruction. (TRE art. II)

Using judicial notice to establish a fact is a questionable method when that fact is to be decided by a jury. Judicial notice is best used to establish the initial reliability of a forensic science or for establishing some more general fact that is clearly not disputable (such as there are seven days in a week). I would be skeptical that the field of GPS and establishing the local of a cell phone at a point in time is the sort of indisputable fact that can just be noticed by a judge.

You should be finding an expert who is knowledgeable in the subject and who can explain scientifically why GPS is accurate. Given that the laws of physics are generally involved, you should be able to make an easy scientific case.

About 4 or 5 years ago, Collin County had a capital murder case in which the defendant's truck was tracked across the country using GPS technology. He picked up the victim in New Jersey, killed her, and dumped her body in N. Texas. I think the perp's name was Brown. Maybe someone in Collin County could assist.

The Collin County case -- Brown v. State 163 SW3d 818 (They used a Collin County person who maps GPS for residences, 911, etc., and an employee of the trucking company that used the GPS to track the trucks). I also used Curry v. State, NO 10-07-00104-CR, 2008 Tex. App. LEXIS 16, (Waco -- 1/2/2008) for support (deputy testified to the use of GPS to map location). It is probably best to get an expert. All I know is the 11th CoA got the .16 m from somewhere -- it wasn't in the testimony (the testimony was feet).