2023-05-17 09:34:00
The Netherlands Forensic Institute (NFI) has investigated whether the recording of floors by iPhones can help police in the reconstruction of crimes. The iPhone’s health app indicates that it registers about ten feet as a floor. The NFI investigation has shown that an important condition is that the user is walking at the same time, otherwise the telephone will not register floors.
The reason for the investigation is a fatal stabbing on the third floor of a porch house in The Hague. The suspect in this case denies any involvement. On the basis of the data in the telephone, the police were able to determine the presence of the man up to the front door of the house, but not inside on the third floor. The phone had only registered two floors.
To test the reliability of the floor registration, the NFI carried out various tests to see which factors influence the accuracy of the registrations. The NFI investigation has shown that an iPhone does indeed register roughly every three meter difference in height as one floor. No physical floors are counted.
It also turned out that Apple’s health app only registers floors when the user walks up. However, iPhones also contain a file that contains temporary information about both floors walked up and down. This file is not visible to a user, but can be extracted from the phone using forensic software.
In the case of the stabbing, it turned out that the registration of two floors matched the scenario that the man walked from the ground floor to the third floor. The height of the third floor was about seven meters, which is two blocks of three meters and a remainder of one meter. “We know that the app counts every 3 meters as a floor, so the number of physical floors does not have to match the number of floors registered by the phone,” says NFI scientist Jan Peter van Zandwijk.
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