During testimony at the Special Tribunal for Lebanon Friday, investigator John Edward Philips explained the appearance of anomalies in the “single-user analysis” theory. The technique, put forward by the prosecution, has been used by investigators throughout the case to demonstrate that multiple phones were likely used by the same person.
Cellular data similar to the information that Philips analyzed has been integral to the prosecution’s case against the five defendants accused of planning and executing the assassination of Prime Minister Rafik Hariri and 21 others in 2005.
Prosecutors have used the movement and coordination between various cellphones attributed to individuals to track the alleged conspiracy leading up to the attack, as well as identify the defendants in the case.
The “anomalies” that Philips discussed Friday centered on several instances before the assassination where phones attributed to one individual appeared to utilize cell sites far apart from each other. At first glance, said Philips, this would indicate that different phones were used by different individuals.
One instance included several calls made on Jan. 18, 2005, where two phones attributed to Salim Ayyash appeared to switch cell towers in quick succession: from one site in Downtown Beirut to another in the southern suburbs.
However, according to Philips, these discrepancies were often the result of irregularities in cell coverage. Citing a previous case he worked on in the U.K. that involved tracking phone calls from an apartment building, he said that, “at the time, the call patterns didn’t coincide with people being in that building.”
Nevertheless, when he actually went to the building and measured the cell signals, he found that “the cell of interest wasn’t the best serving cell site until I got to the floor where the alleged activity was. If you looked at it as a paperwork exercise it would look like an anomaly, but when you went there it wasn’t. On the correct floor, the call patterns were consistent with a single user operating from a single location.”
Philips attributed these irregularities to several factors – including calls originating from top floors of apartments and the behavior of cell signals over large bodies of water. Both factors, according to Philips, could produce odd patterns of call data.
Throughout the rest of the proceedings, Philips used this framework to both identify potential anomalies in the cellular data and then demonstrate why the calls were still consistent with a single user.