SAN DIEGO – As Central Americans from a migrant caravan begin entering the asylum process from the U.S. border, they face a complex legal battle that most who have tried in recent years have lost.

Just under 80 percent of the 15,667 asylum cases from El Salvador were denied from fiscal years 2012 to 2017, according to the Transactional Records Access Clearinghouse, a project at Syracuse University that monitors immigration data through public records requests. About 78 percent of the 11,020 Honduran cases and about 75 percent of the 10,983 Guatemalan cases were denied.

Those trends could change as case law established in the past couple of years has helped more Central Americans show how their stories line up with requirements for asylum.

"There's a steeper hill to climb, I think, in the Central American cases," said Dana Leigh Marks, a spokeswoman with the National Association of Immigration Judges. "They involve cutting-edge legal arguments. The case law is still evolving. Whether it's a liberal or a conservative trend, the reality is law is based on case precedent. The more precedent that builds and makes that principle clearer, the more established it's going to be and the more consistent it's going to be."

Under asylum law, people seeking protection must show that they have been persecuted or have a well-founded fear that they will be persecuted because of their race, religion, nationality, political opinion or membership in a social group.

Being afraid of general violence or rampant crime is not enough to win a case.

Some Central Americans have more traditional cases under the race or political opinion categories, but most are fleeing gang violence or domestic violence. Such cases tend to require asylum-seekers to show that the bad things that happened to them were because they are part of a particular social group.

More are winning their cases than before, said Ginger Jacobs, an immigration attorney in San Diego, especially in the last two years.

Women who could show that they're being targeted because they are women have a better chance of winning their cases, Jacobs said. That could include women who were gang-raped or are victims of domestic violence.

People who can show they fear persecution because their family has been targeted also have a better chance of winning. Members of the LGBT community also have an easier time showing that they're members of a targeted social group.

Judges have started understanding, Jacobs said, how gang violence is intertwined with governments in the Northern Triangle — Guatemala, El Salvador and Honduras.

Having an attorney can also make a difference in how likely someone is to win a case.

About 95 percent of asylum-seekers from Honduras without attorneys lost their cases over the past six years, according to TRAC data. Of those who had attorneys, just over 70 percent lost. People from El Salvador and Guatemala have had similar results.

For some countries, such as China, having an attorney can make a significant difference. Nearly 79 percent of Chinese asylum-seekers who didn't have attorneys were denied protection over the past six years, compared with just under 18 percent of those who did, according to TRAC data.

A TRAC report found that immigration judges from the same court often differ drastically. In San Francisco, where Marks hears cases, the highest grant rate is 97.1 percent and the lowest is 9.4 percent. In Los Angeles, the highest is 29.4 percent and the lowest is 97.5 percent. In San Diego, the high and low are 88.1 percent and 46.2 percent.

"Credible testimony alone can be sufficient if it's consistent with a country's conditions," Marks said. "That's part of why grant or denial rates among different judges vary so much. It's very hard to specifically pin down what is enough to meet your burden of proof."

Matthew Holt, a San Diego immigration attorney, said he thinks about Central American cases as "gang plus," meaning there's gang violence involved plus the person has a characteristic or took some kind of action to make him or her part of a protected group that is targeted by the gangs.

"The Central Americans we're seeing, they're children, youth, young adults, lots of females and small business owners," Holt said. "These are all these people that are trying to get ahead and they can't because the gangs in Central America are murdering them."

Holt said attorneys and asylum-seekers have to keep fighting to make case law that protects the vulnerable, but he said he worries that the process would be too slow for many fleeing danger.