Yes, I heard about this a few days back.
Here's my thoughts:
I don't see a problem with requiring somebody to verbally invoke their right to remain silent. Also, remaining silent works just as well.
However, when you don't remain silent, whether or not you have "invoked" your right to remain silent, then all bets are off.
Look at it this way... Lets say I verbally invoke my right to remain silent, and immediately after provide a full confession for a crime. Does that mean my confession has to be thrown out?
Whether he verbally invoked his right to remain silent or not, all he had to do was actually excercise that right, and not answer any questions or admit to anything.
This is just more extreme nonsense that has been getting this country into worse and worse shape. "Oh, you spelled the mass murderers name wrong on the warrant? Gee... let him go then..."