Please see: An Overview of Drug Crime Defenses in the Commonwealth of Massachusetts.
Most drug charges begin with the underlying offense of possession, and then pile on additional elements in order to impose additional penalties. You read about common defenses to the charge of simple possession in An Overview of Drug Crime Defenses in the Commonwealth of Massachusetts including defenses focusing on whether the Commonwealth can prove actual possession or control, and ways in which to keep certain evidence from being admitted in the case against you.
Proving Intent to Distribute
The additional charge of intent to distribute is commonly based on the way the drugs are packaged, what the police consider "paraphernalia," or the sheer volume of the drugs involved. There are, however, problems with each of these theories. Someone could buy many packages of a drug meant for personal use. "Paraphernalia" often amounts to nothing more than the ordinary implements for consuming drugs. People sometimes possess large amounts of a particular drug to avoid having to expose themselves to the dangers of multiple purchases.
Distribution
To prove distribution, the Commonwealth has to show beyond a reasonable doubt that an exchange took place. Unlike the charge of conspiracy which can cover weeks months or year, distribution happens once at a single instant. In cases where drugs were sold to an undercover witness, the proof is not difficult, but in cases where the Commonwealth seeks to prove distribution by observations or circumstantial evidence, it is often difficult for it to get past reasonable doubt.
Penalties
The penalties for possession with the intent to distribute depend on the class of drug involved, but all include both jail time and loss of license. Further, a conviction for possession with intent to distribute on your record can prove extremely detrimental to your chances of getting a job or other benefits in the future, can dramatically increase the potential penalties for any later offenses. All indications are that the collateral consequences of a conviction for possession with intent to distribute are only going to increase with future legislative actions.
See: G.L. c. 94C; License Suspensions; An Overview of Drug Crime Defenses in the Commonwealth of Massachusetts.