An almost elementary, but laborious digital forensic analysis of mobile phone calls helped the police on Monday crack the break-in at a jewellery showroom at Balaramapuram early on April 29.

B.S. Sajimon, Circle Inspector, Neyyattinkara, said the break-in occurred sometime between 9 p.m. on April 28 and 5 a.m. on April 29.

The police verified each and every call (which was transmitted from and received by at least three cell phone communication towers in the vicinity of the scene of crime) during the eight-hour time window.

They found that some of the calls were from mobile phone connections initiated in Jharkhand and Bihar. They tracked the usage history of the suspect mobile phones, including their ‘handshaking signals' with various towers.

Since mobile phones, unlike landlines, are associated closely with the relative location of their individual owners, the police could discern movement of the suspects before and after the crime.

Investigators said that data from the mobile phone towers, sourced from the service providers, showed that the suspects had visited Balaramapuram several times before the actual heist.

Calls to local contacts

They also learned that the suspects had called some local contacts of theirs, all of them migrant labourers living in labour camps at nearby Uchakada and Mukkola. The police detained them and found the identities of the suspected burglars.

Deputy Superintendent of Police P. Gopakumar said the gang comprising eight members, three of whom were arrested on Monday, had arrived with drilling tools, a gas cutter, and oxyacetylene cylinders from Bihar and Jharkhand early this month. They had camped in migrant labour camps in Kollam and Varkala.

The suspects drilled into the jewellery shop through the rear wall. They used the gas cutter to cut open the iron chest where the bulk of the gold ornaments were stored. The jewellery owner reported a loss of gold ornaments weighing almost 2.5 kg.

Migrant labourers

Mr. Gopakumar identified the arrested persons as Arjun, 32, Deepu Sharma, 26, and Guddu, alias Arjun Singh. All are residents of Bihar and primary school dropouts. They worked as manual labourers and lived in labour shelters at various construction sites.

The accused were produced before the court on the charge of theft, trespass, and conspiracy and remanded in judicial custody for 14 days.

The police said efforts were on to arrest the rest of the gang and recover the loot. Sheikh Darvesh Sahib, Inspector General of Police, Thiruvananthapuram Range, and A.J. Thomaskutty, Superintendent of Police, Rural, supervised the investigation.