Delhi

Using call detail records to track down criminals

Call detail records have become an important investigative tool, say officers.

Call detail records have become an important investigative tool, say officers. | Photo Credit: File Photo

Priyanka (name changed), a resident of Uttam Nagar, lodged a complaint with Dwarka’s Cyber police station in April this year, alleging that an unknown person had created her fake Instagram profile where the accused was posting her pictures and sending obscene messages to her followers.

As a result, Priyanka was receiving calls from her Instagram followers soliciting physical relationships in exchange for money. The police lodged an FIR under IPC sections pertaining to stalking and constituted a team to trace the accused.

Among the investigating tools that the police used to track the accused’s exact location, the accused’s call detail records (CDR) played a vital role. Police managed to track his mobile number, through which they contacted the service provider and obtained details about the calls made by the accused as well as their time and duration. 

The location of the accused, later identified as Ankit Kumar, a B.C.A. student, was tracked to Uttam Nagar, from where he was arrested following a raid. 

In solving cases such as Priyanka’s, the Delhi police have made heavy use of CDR, among other intelligence tools like IPDR (Internet Protocol Detail Record) and the IMEI (International Mobile Equipment Identity) of a phone. 

IPDR allows the police to track call details made through social media applications such as WhatsApp and Telegram, a mode of communication that is increasingly being used by criminals. Meanwhile, IMEI is a unique number for identifying a device on a mobile network.

Senior officers said CDR has acted as the primary probe tool that helps them recover the accused’s location by zeroing in on the network tower through which the accused made their last call. 

“A mobile tower generally covers a distance of 50 metres in radius. The service providers often share with us the longitude and latitude within the tower’s radius under which the call was made,” an officer said explaining how CDR tracking works.

“To access the accused’s CDR, once a crime is committed or after recovering their phone following an arrest, a DCP-rank officer sends a formal request to the network provider under section 91 of CrPC, asking it to provide call details which can go back up to a year, which is the maximum period for which the company holds a person’s call information,” the officer said.

CDR also contains details about the exchange of SMSes on a phone. It, however, does not include the contents of the communication.

“While the CDR does not record the contents of the telephonic conversation, the call details of the accused give us just enough information about their whereabouts and their probable accomplices during the time of the incident,” another police officer said.

The officer added that an accused could be in touch with dozens of people while they are conspiring to commit a crime. “Once we intercept an accused’s calls, we are led to the co-accused as well,” the officer added.

Sources added that the time required to recover CDR depends on a case-to-case basis.

“Generally, we send a request to the mobile company on an urgent basis so that we obtain the CDR and use it with other intelligence tools at our disposal to nab the accused. Most often, they (service providers) provide the details within an hour. But sometimes it takes more than a day,” the source added.

Losing relevance

The police officers added that while the CDR has become an important investigative tool, most criminals are now switching to social media applications such as Telegram and WhatsApp to communicate with their accomplices, details of which can only be obtained through IPDR.

“While IPDR does help trace the details of communication that happens through applications like WhatsApp and Telegram, it is not as accurate when it comes to tracing the precise location of an accused,” said an officer. 

The officer added that while even CDR could lead to inaccurate inputs at times, in most cases, the CDR helps the police establish the link between a crime and the criminal alleged to have committed it, as it helps police gather more incriminating details about the accused on the basis of their call information.

Evidentiary value 

In order to build its case before the court, the police attach the accused’s CDR, as part of electronic evidence against them, to the chargesheet. 

The Magistrate accepts the same only when the guidelines laid down in a Supreme Court judgement, in the 2014 PV Anvar v/s PK Basheer case, are followed. 

A senior police officer said, “Court holds CDR to be of great value but it cannot be the sole evidence to implicate an accused, as the calls have to lead to recovery of some physical evidence or an incriminating confession”.

In the Delhi riots cases, courts have primarily taken note of the CDR of the accused persons while passing bail orders and judgements. 

In most matters, the courts have granted bail to the accused after observing that the accused’s CDR reveals that he was not at the place of incident or even in its vicinity during the time when riots broke out. Advocate Dinesh Tiwari, who is representing several Delhi riots accused, said: “In several cases, court has also granted bail after observing that the accused resides near the place of the incident and hence his CDR ought to show the same location”.


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Printable version | Jul 4, 2022 10:19:18 am | https://www.thehindu.com/news/cities/Delhi/how-police-are-using-cdr-to-track-down-criminals/article65596488.ece