Illegal alien

From back cover Ace paperback January 1999:

When a disabled spaceship enters the Earth's atmosphere, fear is quickly replaced with awe. Seven members of the incredibly advanced Tosok race are welcomed by the world with open arms, and the people of Earth put their best face forward. Then a popular scientist is found murdered. All evidence points to one of the Tosoks. For the first time, an alien is tried before humans in a court of law. And in the unprecedented trial, where two cultures clash, there may be far more at stake than the accounting for one human life...