Sexual assault survivors know it. Prosecutors know it.  

And a high-profile case has make it clear to many more people: It is remarkably hard to secure a conviction in a sexual assault or rape case in the U.S. 

The methods used to secure Harvey Weinstein's conviction in New York were always controversial, experts say. So the fact that it was overturned didn’t shock some legal experts. 

Prosecutors essentially bolstered the case against Weinstein by using the testimony of multiple accusers alleging crimes he was not charged with. An appeals court ruled that was a violation of Weinstein's rights because it unfairly biased the jury against him.

Weinstein’s lawyers hailed the decision, with attorney Arthur Aidala telling reporters outside Manhattan Criminal Court that “the law was not applied fairly.”

Reactions from sexual assault victim advocates were more complicated as they measured their thoughts on the legal technicalities at play alongside their feelings about the big picture.

“At the moment, it can feel like a setback when the conviction has kind of stood in for criminal accountability in the #MeToo era gets overturned,” said Deborah Tuerkheimer, a Northwestern law professor and author of the book "Credible: Why We Doubt Accusers and Protect Abusers.”  

But the movement “was never about Weinstein as an individual; it was about systemic change, and it continues to be about systemic change.” 

When it comes to the criminal justice system, any systemic change faces daunting realities: 

• Many sexual assaults aren’t reported and aren’t witnessed 
• Juries may misunderstand sexual assault  
• There are well-established legal protections for people who are on trial that are uniquely challenging in cases of sexual assault 

Weinstein will remain incarcerated (he was also convicted in California and he may be tried again in New York). But the case against him reveals challenges that span the criminal justice system.  

Many sexual assaults aren’t reported

Very few rapes get reported to law enforcement, and fewer still ever lead to an arrest and conviction. Out of every 1,000 sexual assaults, just 25 perpetrators will see jail time, according to the Rape, Abuse and Incest National Network (RAINN). According to the Centers for Disease Control and Prevention, over half of women and about one-in-three men have experienced some form of sexual violence in their lifetimes, but researchers know numbers are underestimated. 

Advocates and experts say long-existing biases and stigma against survivors makes them less likely to come forward, and even when they do, authorities rarely pursue charges against an assailant. 

Juries, legal system may misunderstand sexual assault

Prosecutors have to prove crimes beyond a reasonable doubt, and with sex crimes, they consider how juries will react, said Tuerkheimer, who used to be a New York prosecutor for domestic violence cases. 

But the criminal justice system, and society members who make up juries, often rely on old myths about rape — such as that they are usually committed by a stranger jumping out in a dark alley, said Beth Posner, professor at the University of North Carolina School of Law and director of the Domestic and Sexual Violence Clinic. 

Harvey Weinstein timeline:The disgraced movie mogul's legal battles before NY conviction overturned

The circumstances of Weinstein’s trial were unusual, because it involved factors that would usually dissuade prosecutors from going forward with a case. Weinstein knew the accusers. The accusers also in some cases had ongoing communication with Weinstein after the assault, or engaged in a consensual relationship with him at other times. They also didn’t come forward about their assaults right away. 

“The way this happened, what Harvey Weinstein did, this is the reality, it’s the truth, but it’s just not easily packaged … Prosecutors of course want to see things easily packaged,” Posner said. 

Anything that can make a victim seem less credible is a reason for a prosecutor not to take up the case, even if evidence of guilt seems overwhelming, Tuerkheimer said. 

“We come to the task of judging credibility primed to disbelieve. We see that outside of the courtroom, and we see that inside the courtroom,” she said. 

Well-established legal protections for people who are on trial

Defendants have a right to be judged on the facts of the case at trial, and there’s strong legal protections against bringing up previous allegations, with limited exceptions that can split the legal community.  

Posner, who agrees with the appeals court's decision to overturn Weinstein's conviction, said it’s important for a court of law to preserve the right of a defendant’s innocence until proven guilty: “Even the most awful human being is entitled to constitutional protections.” 

But that creates a unique legal problem for prosecuting rape cases that already have a slew of legal challenges. As in Weinstein’s case, it would be easier for prosecutors if they could tell jurors about a pattern of allegations. 

“Why is that necessary? … Because people don’t generally believe women,” Posner said. She said prosecutors may have feared that a jury wouldn’t believe the accounts of those three on their own, and with little concrete evidence. “Why can't a jury believe these three women and the stories that they had to tell? That's the terrible, unfortunate thing about this case.” 

The discrediting of accusers remains a problem in prosecuting sex crimes, experts said, because courts and juries need much more education on what rape is and the reality of how survivors behave. She and Tuerkheimer both said if women’s credibility were judged fairly, additional bad acts witnesses wouldn’t be needed to help get a conviction. 

What does all this mean for survivors?

The decision to toss the conviction revealed to the sex crimes legal community just how important it is to educate courts, judges and juries about the realities of rape. More experts on sexual assault, mental health and public health should testify in courts, Posner said.

Posner said the decision could cause even fewer women to report their assaults, at least in the short term, and might cause some prosecutors to bring even fewer cases to trial for fear of having a conviction overturned. 

“To be a survivor looking at the world, watching the news, and seeing that you can do everything right – you can tell your story, you can have all of these people standing behind you, a whole #MeToo movement behind you – and still, the guy gets off. That is such a horrible blow to the minds and spirits of individual survivors, and the movement,” Posner said. 

'Absolutely devastated':Harvey Weinstein accusers react to rape conviction overturning

But experts also said the latest news shouldn’t eclipse all the hard-won gains in societal understanding of the pervasiveness of sexual assault that came after those first allegations against Weinstein. And though it is a blow to survivors, she said it will mobilize advocates to help survivors connect to resources.

“The bravery of the survivors who came forward and who shared their stories, that bravery was not changed by anything that happened,” said Emily Martin, chief program officer for the National Women’s Law Center, which joined an amicus brief opposing Weinstein’s appeal. 

“The impact of those survivors coming forward and sharing their story was always much, much bigger than any criminal conviction.” 

Contributing: Marco della Cava and David Oliver, USA TODAY