Scheck compared that deterioration, caused by bacteria breeding in moisture, to milk turning sour.
And, in a dramatic series of questions supported by a videotape of Fung at the crime scene, Scheck showed the criminalist handling what may be an important piece of evidence with his bare hand - despite Fung's insistence that it did not happen.
That particular piece of videotape had been turned over earlier to the prosecution - on the tail-end of a tape of other evidence - but either none of the three prosecution lawyers in court yesterday had viewed that part of the tape, or none realized its signficance, because all three appeared surprised and irritated when it was played.
Also yesterday, the defense filed a motion asking Judge Lance Ito to investigate whether the prosecution was selectively investigating jurors to get those biased toward Simpson removed from the jury.
In the same motion, the defense said it did not want Ito to dismiss any other jurors without a full hearing on whether there is enough legal cause for the dismissal. So far, six of the original jurors have been dismissed, leaving six alternates available.
And it asked that civil employees, such as social workers, replace sheriff's deputies as guards and escorts for the jury.
The motion was in response to the dismissal last week of juror Jeanette Harris. In interviews after her ouster, Harris said - among other things - that the jury was dividing along racial lines and that sheriff's deputies treated white jurors and black jurors differently. Harris has been ordered to meet with Ito in his chambers this afternoon.
Yesterday's session had started on a much lighter note, when prosecutor Marcia Clark - whom a friend describes as "more recognizable than Madonna" - arrived outside the courtroom sporting a new hairstyle. The waiting spectators oohed and aahed and applauded, while Clark smiled broadly and turned a pirouette before going into court.
Even Ito took notice. After acknowledging the defense team, he turned toward the prosecution table.
"People represented by," he started, then seemed momentarily nonplussed. ''Miss Clark?" he said, his voice lilting upward as spectators laughed.
That was probably the last pleasant moment in the court day for Clark.
Fung looked weary and grim at the start of his fourth day on the witness stand, with dark circles under his eyes, his shoulders slumped, his hands clasped between his knees.
It was a posture that members of the prosecution team, listening helplessly to Fung's testimony, soon adopted as well. Simpson and his defense team, by contrast, radiated satisfaction. A slight smile flickered often across Simpson's face as he listened to Scheck's cross-examination.
As the day wore on, Fung sighed often and seemed to have trouble coming up with the words to answer the questions put to him by Scheck.
Fung still faces additional questioning by the prosecution, after which Scheck gets the opportunity to grill him again.
Within 45 minutes, Scheck made Fung admit that evidence in Nicole Brown Simpson's courtyard had been moved around before Fung and his assistant had finished collecting samples.
Scheck then moved on to questions about Fung's truthfulness on the witness stand, by asking him whether he had any suspicions the day after the slaying of Nicole Simpson and Ronald Lyle Goldman that evidence had been moved.
When Fung insisted that he had not had those suspicions, Scheck produced Fung's crime scene report - in which the questions "Has the scene been altered? If so, by whom and how?" were answered not with the word no, but with a question mark.
And Scheck caught the prosecution team, as well as Fung, by surprise with a videotape that seemed to show Fung at the murder scene taking hold of an envelope - possibly the envelope containing glasses that Goldman was returning to Nicole Simpson - with his bare hand.
Moments earlier, Fung had repeatedly denied touching the envelope with an
"Did you touch that envelope with your bare hands while collecting it, Mr. Fung?" Scheck asked.
"No," Fung replied.
"Sure of that?" Scheck probed.
"Yes," said Fung.
"No question about it in your mind?" Scheck said.
Fung held fast, even after Scheck played and replayed the portion of tape in which a man - who Fung acknowledged was he - took a white object the size and shape of the white envelope containing the glasses. That envelope, in a protective plastic bag, was passed among the jurors.
Ito ordered the tape played backward, frame by frame, until the object came into focus. When it did, there was an audible gasp of recognition from several spectators.
As the jurors passed around the actual envelope, they looked up at the screen for comparison. And then each one of them picked up the notebooks in which they are allowed to keep notes and began writing.
In what may ultimately prove to be key testimony for the defense - in that it will allow arguments about the results of DNA testing - Scheck questioned Fung closely about the way blood evidence was collected and stored.
He covered everything from how often criminalists changed their latex gloves (when they looked dirty, not between collection of every sample), to how tweezers used for collecting bloody swatches were cleaned (with distilled water and "chemswabs"), to how the swatches with blood samples were carried back to the lab (in plastic envelopes, inside paper envelopes).
Scheck handed Fung a series of textbooks and manuals detailing how fresh blood samples should be handled. Each said that the samples "shall not" or ''should never" be packaged in plastic.
"So is it your position that it's sound practice to put a wet blood stain in a plastic bag temporarily?" Scheck asked.
"That's the way I was taught and trained to do it in the Los Angeles Police Department, yes," Fung said.