Prosecutors thus far have tried to show that O.J. Simpson had the motive and opportunity to kill his ex-wife and her friend.
Now, they plan to produce scientific evidence directly linking him to the murders.The next few weeks - and possibly months - of the trial promise a parade of police technicians, laboratory workers and expert scientists, starting with today's testimony by police criminalist Dennis Fung.
They will delve into the intricacies of evidence collection, cataloging and storage, as well as the minutiae of microbiology.
In a word, dull. But that's not to say it won't be important.
The prosecutors' case is built on the strength of its scientific evidence - sophisticated genetic tests to prove that Simpson left his own, unmistakably unique blood at the crime scene.
Other physical evidence includes bloodstains in Simpson's Bronco and on a pair of socks in his bedroom that prosecutors say match the blood of Nicole Brown Simpson. Authorities also say tests found blood from Ronald Goldman in the Bronco and on the glove found beside Simpson's house.
"This is the crucial phase of the trial," said Loyola University law professor Laurie Levenson. "Witnesses may forget or may be biased, but scientific evidence usually leaves a strong impression on jurors if they understand it."
In this case, that's a big "if."
Prosecutors have the challenge of trying to keep jurors interested while leading them through technical, scientific evidence.
The defense will seek to show that police were so sloppy in picking up blood, hair and fibers that even if the subsequent DNA tests were properly done, the results were botched because of contaminated samples.
The defense also will argue that the tests themselves were conducted improperly and that many of the techniques are too experimental to be trusted in a court of law.
Until now, prosecution testimony has centered on motive and opportunity.