Four Corners: July 15

Monday’s Four Corners screens a PBS documentary from the US on the Boston marathon bombing and how the case was solved.

At 2.49 pm on 15th April this year, two bomb blasts turned the Boston Marathon finish line into a scene of carnage. The blasts left three people dead, hundreds injured and a city gripped in fear. How did the investigators turn the chaotic physical evidence at the scene of the crime into a coherent trail of clues that would lead them to the killers?

This week on Four Corners, PBS’ NOVA documentary producer, Miles O’Brien, looks at how the events unfolded on the day of the bombing and he tracks how a team of investigators used modern technology, combined with good old fashioned detective work, to break the case.

O’Brien begins his investigation by travelling to New Mexico where experts are able to test explosives and bomb casings to work out what kind of bomb might have been used. Using slow motion footage, the bomb blasts on the testing range are matched to a film of the Boston bombs. Smoke plumes are analysed and bomb fragments are matched.

Bomb matching though is just one of the techniques used to track those involved in the attacks. Closed circuit television footage and mobile phone photos provide pictures of potential suspects carrying bags that might conceal a bomb. In turn, those images are computerised and fed into facial recognition technology in an attempt to match them with known criminals or persons of interest. It is painstaking work but it is the best way to find out exactly who the police are looking for.

The program also looks at the use of satellite tracking systems, mobile phone triangulation software and the use of infra-red cameras that can locate people hiding in built-up areas.

On a less positive note, the report found that social media created problems for the police investigation, forcing detectives to release photos of the suspected bombers earlier than they planned. Initially police held off releasing photos of the suspects fearing they might flee or commit further acts of violence. In the end they were forced to act when individuals and media organisations began posting photos of innocent citizens, claiming they were suspects in the bombings.

Ultimately, though, it paid off. Less than five days after the bombing, the key suspects were identified. After a shoot out involving police, one was killed and the other was finally taken into custody after a massive manhunt.

8.30pm on Monday 15th July on ABC1.