The man was asked to testify Monday regarding text messages he sent and received on the night in July 2016 that he encountered Spacey at a Nantucket restaurant. Spacey's lawyer contends that the young man had deleted text messages that could back up Spacey's assertion that whatever happened that night was consensual flirtation.
After the lawyer, Alan Jackson, told the man he could be charged with a felony for deleting evidence, the man invoked his constitutional right to protect himself from self-incrimination.
Judge Thomas S Barrett of Nantucket District Court then said the case "may well be dismissed" if the accuser continues to refuse to testify.
"The case revolves around this individual and without him the commonwealth will have a tough row to hoe," Barrett said. He did not dismiss the case Monday but gave prosecutors a chance to decide how to respond to the accuser's invocation of the Fifth Amendment.
Spacey, 59, who was not in court Monday, faces one count of indecent assault and battery. He is accused of rubbing the young man's penis at a Nantucket restaurant called the Club Car, where the man, who was 18 at the time and is now 21, was working as a busboy.
In trying to prove Spacey's innocence, the defense lawyer has sought access to the man's phone, but last month, the man's lawyer, Mitchell Garabedian, told the court that the phone was missing. Barrett had ordered that if the phone could not be located by Monday, the young man and his parents would have to appear in court to explain its whereabouts.
In the courtroom Monday, Jackson grilled the accuser about the missing messages. The young man said he had noticed that a part of a text conversation was missing but that he did not know how it disappeared.
Jackson then asked the young man whether he realised that altering evidence that could be used in a prosecution is a felony punishable by prison time.
The hearing then went into a break. Afterward, it was announced that the accuser would be pleading the Fifth.