First, here is a useful summary of your Constitutional rights.
Now we come to the core concept and the prime directive:
Say as little as you possibly can consistent with remaining calm and civil. Anything you say — and when it comes to establishing what you said it is what the police officers say you said that counts — can and will be used against you in and out of court. Verbal utterances alone can trigger an arrest, if in the view of the police on the scene those utterances mean you are being “disruptive”. We suggest that you print and carry a copy of this card and let it do your talking for you.
Note that while in general you do have the right to refuse to identify yourself there is one very important exception to this: you must show your license and registration when stopped in a car. In other situations, such as in a park, you can refuse to identify yourself.
If you wish to refuse consent to a search, which is always a good idea, do so politely but explicitly. Say ‘I do not consent to a search’. (Not inviting someone in is not the same as not giving consent to a search, if you see what we mean.) If the police say they have a search warrant, ask to see it.
Remember the prime directive: Stay calm and do not interfere with or obstruct the police in any way. Getting you to be obstructive or disruptive is what they do, because once they have you there they have you. The courts will always side with them. Nothing will annoy them more than if you stay polite and calm. Boiled down to a single line: You can refuse but you cannot resist.
You probably need an attorney more than you think you do, especially if you plan to plead guilty or are navigating the “admitting to sufficient facts” process*.
Occasionally an officer will confiscate your stash without arresting you. They might tell you that you will be “getting something in mail”. This might mean:
1) Nothing. While not the most likely scenario, it certainly happens that for whatever reason the officer never processes the case.
2) You receive a notice from the local district court advising that a criminal complaint application has been filed against you and notifying you that it will hold a hearing on a specific date and time. This hearing is a statutory right because you were not arrested. If you are being charged by the federal authorities (National Seashore) the letter will be sent from the U.S. Attorney’s Office in Boston.
3) You receive a notice from the local district court summonsing you to appear to be arraigned on the charge.
In the case of 2) or 3) you will probably need an attorney.
*Note that Massachusetts allows conditional release for people facing their first prosecutions. This procedure is referred to as an “admission to sufficient facts” and also as a “continuance without a finding of guilt”. It allows you to opt for probation rather than trial. In theory, if and when you complete probation (successfully), your record is supposed to be “expunged,” ie, will not reflect the charge.
Terms of probation may likely include random urine tests. The probation officer is not required to revoke your probation on your first positive test. He or she need not tell you of your failure (which means that your second failure might come as a surprise). Failing probation will likely result in a guilty finding being entered on your record.