Satnav data enabled gardaí to track movements of suspect’s vehicle

Data allowed gardaí to narrow focus of search for Jastine Valdez

A video clip has emerged on social media showing Mark Hennessy on the day he purchased the SUV suspected to be the vehicle used in the abduction of Jastine Valdez. Hennessy was shot dead by gardai in Cherrywood Business Park on Sunday.


Gardaí were able to use data stored in the satellite navigation (satnav) system of the Nissan Qashqai driven by 40-year-old builder Mark Hennessy to track the vehicle’s movements from Saturday evening.

Knowing where the vehicle had been during that time allowed the gardaí to narrow the focus of their search for his victim, Jastine Valdez to Killiney and the area around Rathmichael in south Dublin.

Valdez was abducted near Enniskerry, Co Wicklow, though her body was found yesterday little more five miles away in Rathmichael, while Hennessy met his end a few miles further on at Cherrywood, Co Dublin.

The satnav, which maps routes for drivers, operates by using satellites intended originally for military use. A connection between the satnav in the vehicle and three satellites has to be achieved for the locater system to operate.

Data is stored for a time in the satnav records where the vehicle has been at any given time, noting the GPS co-ordinates.

“To retrieve the data, all you have to do is put a UBS stick into the back of the satnav and download the information,” explained a vehicle data retrieval expert yesterday. “Then you upload it on to a computer and you have what is a live stream of the GPS co-ordinates of the vehicle’s positions.”

Asked what period of time was covered by the data retrieved, the expert said about 24 hours. In the urgent search for Miss Valdez, once Mr Hennessy’s vehicle could be searched, gardaí were able to download the satnav data.

Live stream

“You get what, in effect, is a live stream of where the vehicle has been for the previous 24 hours,” said the expert, an academic who asked not to be named. “You can put the co-ordinates into Google maps and see exactly where the vehicle has been.”

Apart from satnav, all modern vehicles also store a wealth of other digital data. Cars and trucks all have numerous on-board computers that are connected by a vehicle’s central cabling system known as Canbus. Since 1994, a standard retrieval format known as European On Board Diagnosis (EOBD) has been mandatory on all vehicles.

Retrieval technology, such as the Bosch CDR (crash data retrieval), a tool that may be plugged into the car and information downloaded, indicates precisely what a vehicle has been doing – with regard to speed, gear usage and use of other items such as brakes, lights and indicators, for example. Data for these can be retrieved for the five seconds before a crash and the two seconds after.

While this technology and know-how exists, it is not used routinely by An Garda Síochána, insurance companies or the courts in seeking to determine what a vehicle has been doing immediately before a contested incident.