Police officers are evidence collectors and theoretically speaking are not supposed to pass judgement of guilt as that is not their role in the legal system. Theoretically, also, police officers are supposed to use their discretion—discretion defined as electing not to act when they are statutorily required; they are to treat all infractions of the law the same—do the crime and pay the dime. Obviously, however, that is incongruent with reality. Officers do exercise discretion and they do pass their own judgements. This creates a tango which officers and civilians dance, as people talk and try to be cooperative in hopes of leniency while simultaneously digging themselves into an ever bigger hole. The strategy does sometimes work but it's playing Russian roulette with your freedom and lady luck doesn't treat everyone the same. In fact, for some crimes such as DUI or weed possession, many states have upfront diversion programs where charges are basically dropped for first-time offenders but it's only available to people who basically desisted and relinquished their legal protections during their incident.
There's a guy I know who once went fishing in a wildlife reserve (or something along those lines). After some while, a plainclothes officer in a boat spotted him smoking weed. So the plainclothes officer strikes up a friendly conversation for a few minutes and meanwhile the guy is waving around a pipe in his hand. Totally busted, right. Well, the guy explained why he was there, how it was a day for him to get away from his wife and be just by himself disturbing nobody. Turns out he was smoking weed on federal land and so the officer couldn't let him go, but because the guy was so personable, explanatory, and cooperative, the officer wrote him a small ticket rather than arrest him. So, it boils down to the personality of the officer, you, the offense, the situation, and sheer luck, but any good lawyer will advise to remain silent. As SmoothTalker said, silence is not evidence of guilt.