Minister of State for Home Affairs Desmond Tan's recent statement on the use of TraceTogether data greatly undermines the repeated assurances given by Foreign Minister Vivian Balakrishnan concerning the privacy of TraceTogether data (Police can use TraceTogether data for criminal investigations, Jan 5).

Mr Tan said the Singapore Police Force, not just the Ministry of Health, may have access to TraceTogether data. This has caused disappointment and resignation in many people.

In the parlance of privacy, using personal data for a purpose other than its original one comes under the concept of function creep.

TraceTogether data is collected for the purpose of contact tracing only, as originally promised by the Government.

To use the data for criminal investigation, while logical and well-intentioned, constitutes function creep, and erodes the trust the Government has built up.

This erosion is not outweighed by the supposed benefits that TraceTogether data brings to criminal investigation.

For one thing, TraceTogether data does not add to the repertoire of investigation tools. Surveillance cameras are more effective and efficient for tracking people movement.

It is also easy to circumvent: A smart criminal can simply turn off Bluetooth and show a fake SafeEntry screenshot.

Worse, by passing his phone or token to an accomplice, the criminal can create a fake alibi by pretending to be somewhere else other than the crime scene.

In other words, TraceTogether data may not be that useful for criminal investigation. But using it in this manner creates suspicion in the public mind regarding the Government's intention in promoting the app and token.

I urge the Government to reverse its decision, and to ensure that TraceTogether data is used solely for contact tracing.

Terence Sim Mong Cheng (Dr)