Ferguson policeman Darren Wilson stays silent and out of sight

One morning late last month, a US court filled up with prosecutors, lawyers and press who wondered if they would catch a glimpse of a vanished man.

The man, police officer Darren Wilson, had not been seen in public since August 9, when he shot and killed an unarmed black teenager in Ferguson, Missouri, and found himself in a wave of national fury.

But here, at this unrelated preliminary hearing in St Louis, Wilson had incentive to appear. He had been asked to show up to provide testimony against an alleged low-level drug dealer - somebody he had wrestled to the ground and handcuffed 20 months earlier, in an arrest that won him a Ferguson city commendation. Now Wilson just had to recount the story to a judge.

The players took their places for just one in a series of rapid-fire hearings. A few minutes passed. The judge called the lawyers into whispering range, and soon it became clear: Wilson was not going to show, his absence emblematic of a remarkable period in which the central character of an explosive national story has gone totally silent and disappeared from public view. Judge Mary Schroeder then dismissed the drug case for what she called a "failure to prosecute".

For 3½ months, Wilson has been the officer that almost everybody has an opinion on and almost nobody knows. With a grand jury set to determine as soon as this weekend whether Wilson's shooting was justified, the 28-year-old white officer has not given a public account of what transpired before Brown's death. Neither have his lawyers.

Experts and lawyers familiar with other racially charged cases said Wilson has no obligation to speak publicly - and even doing so might not change many opinions after the volatile protests that followed Brown's death.