The key in your sentence is "investigation". If an investigation is ongoing...then you do have the right to be silent and it should be used if possible. The problem is when people try to "remain silent" when they are required to answer "non-incriminating" questions. Those should be answered tactfully and carefully.

Dont get me wrong, Im not trying to be an ass...just make sure the right info gets out. When I was patrol...if someone were to just refuse to answer any and all question (be a dick) then I also would not be as friendly. 9 out of 10 times that person ended up in jail for one reason or another. Just remeber Obstruction of Justice is a catch all charge and is used widely for situations were people are being "not nice". And yes those stick in court.

if I was drunk and got pulled. I would be respectful and answer the basics. If it turns into a Dui investigation . Then I would refuse to do all test. I would go to jail for fail to submit/comply with field sobreity. Post my bond and get an attorney (not public defender).

not many people in my proffession that dig mustangs...lol