She has been described by friends as a "brilliant" student, eager to pursue a research career in medical anthropology. He was responsible for cleaning mouse cages in a university lab.
Authorities have not yet pinned down a motive for the killing -- in which Clark was accused of murder after Le's body was found hidden in a laboratory wall on Sept. 13, the day she was to be married.
New Haven, Conn., Police Chief James Lewis told The Associated Press officials may never know why she was killed.
"The only person who knows the motive is the suspect," Lewis said. "It's true in many cases. You never know absolutely unless the person confesses, and in this case it's too early to tell."
Brad Garrett, a former FBI agent and an ABC News consultant, said the fact that Le was found strangled may hint at a motive in the case.
"People who kill other people and strangle them is a very personal thing because they are actually looking at you as they are dying," Garrett told "Good Morning America Weekend." "Think about what anger and rage anyone would have to have."
If Clark committed the crime he is accused of, a criminologist told ABCNews.com his actions might be explained by what sociologists call "relative deprivation."
That psychological mind set can be triggered "when you are measuring your own self worth against others and you come out on the bottom," according to Northeastern University criminologist Jack Levin, who has been following press accounts of the case.
"[Ray Clark] worked in an Ivy League school where most of his co-workers were potentially successful and had advanced degrees and were looking forward to a fulfilling and happy life," said Levin. "He was cleaning cages."
Le's research on enzymes could have had involved breakthroughs in cancer, diabetes and muscular dystrophy. Clark's work, on the other hand, tidying floors and cages, was more janitorial in nature.
Ann Turner, executive director of the American Association for Laboratory Animal Science, told the Hartford Courant "there is a gulf" between technicians and the researchers they interact with, but that gap would not necessarily led to tension.
"If there is a culture of trust and a culture of respect, the researchers will respect the animal care technicians, and vice versa," Turner said.
Since his arrest Sept. 17, Clark has not entered a plea and neither he nor his lawyers have not spoken, but police say evidence is mounting against the suspect in what they are calling a case of workplace violence.
Some friends told ABCNews.com said they could not imagine Clark -- "a nice guy" -- committing a crime. Others who knew him, however, described him as a "control freak" who was competitive in sports, compulsive about his work habits and controlling in his romantic relationships.
One law enforcement official who talked to the AP on condition of anonymity said this week that Clark's co-workers said he was territorial about the mice whose cages he cleaned.
The psychological need for control is often "underestimated as a motive for murder," according to Levin.