He was living in Virginia Beach, and had an indoor pot growing operation with about 120 plants. Somehow (he didn't say how) he was caught and charged with production with intent to distribute. But the pot that he was growing was for his personal use -- he hadn't planned to give or sell it to anybody else. He decided to plead not guilty and take the case to trial.
As it turns out, Virginia (at the time) did not have any arbitrary limit for distinguishing personal use amounts and distribution amounts. (In New York, by contrast, anything over 25 grams is considered to be intended for distribution.) In other words, if he could prove that all 120 plants were for his personal use, he would be convicted of the lesser crime of possession rather than distribution. He decided that he would prove this.
At the trial, the prosecution called the police to the stand, who testified that they had confiscated 120 plants and that each would produce about a pound of dope, and that 120 pounds was clearly an amount that was intended for distribution. My friend then cross examined them. He asked how they arrived at the estimate. He asked if they had taken into account the stage of maturity of the plant. He asked if they could identify how much of each plant was smokable and how much was not. They were unable to provide answers. They really hadn't considered any of that.
Then my friend took the stand to testify on his own behalf. He is a big man with very long hair, beard and mustache. He spoke with great expertise about growing pot, how much time it takes to grow a plant, how the budding cycle works, which parts of the plant are smoked and which are not. He arrived at an estimate that each plant had about .25 ounce of smokeable bud on it at the time that they were confiscated. Then he went on to describe his personal use. He talked about how pot is extremely physically safe to use, and that since no amount of smoking could really hurt him, there was really no upper limit on what could be considered personal use. Then he talked about how he loved smoking it, that he did it all the time, every day. He estimated how much he smoked in an average day. (Remember, a pack of cigarettes weighs about an ounce, and so a person who smokes an eighth or less a day doesn't sound very shocking in comparison.) In the end, he concluded that his plants would have provided him with about 4 - 6 months worth of pot, which he would happily smoke, knowing that he had produced it more cheaply than if he had bought it on the street, and that he had avoided becoming involved in the criminal drug trade by doing it on his own.
The jury found that the 120 plants were for his personal use, and he received a slap on the wrist.