Six people have brought a landmark class-action lawsuit against the Los Angeles County Sheriff's Department (LASD) Friday on grounds they are or were illegally detained in the jails and stations of Los Angeles County Jail for days, weeks, or months after they were entitled to be released because they are the subject of "immigration holds."

Immigration holds, sometimes called "immigration detainers," are notices issued by the U.S. Immigration and Customs Enforcement (ICE) requesting that an individual in local custody be held pending further action. Unlike warrants, they are issued without any judicial determination of probable cause, and they are frequently issued in error.

The lawsuit reveals the serious civil rights violations against tens of thousands of foreign nationals who have been detained in the United States.

Immigration detention in the United States has reached crisis proportions. In 2011, the U.S. Department of Homeland Security (DHS) held a record-breaking 429,000 immigrants in over 250 facilities across the country, and currently maintains a daily capacity of 33,400 beds, even though, in the overwhelming majority of cases, detention is not necessary to effect deportations and does not make the United States any safer, according to the American Civil Liberties Union (ACLU).

Among those unnecessarily locked up are survivors of torture, asylum seekers, victims of trafficking, families with small children, the elderly, individuals with serious medical and mental health conditions, and lawful permanent residents with longstanding family and community ties who are facing deportation because of old or minor crimes, according to ACLU.

ACLU claimed that the U.S. lock-up system is a massive waste of taxpayer dollars, costing 122 dollars to 164 dollars to hold a detainee each day, or 2 billion dollars a year. Adding insult to injury, detainees are exposed to myriad abuses -- from a lack of adequate medical and mental health care that has caused unnecessary deaths to rape and sexual abuse.

The lawsuit filed against LASD by ACLU in Los Angeles addresses two related practices of LASD, including detaining people beyond their release date solely on the immigration hold and refusing to allow pretrial detainees to post bail to secure their release from jail if they have an ICE hold.

According to ACLU, some 2,100 inmates each day (or 14 percent of the daily jail population) have ICE holds lodged against them in the Los Angeles County Jails. These inmates spend on average nearly three weeks longer in L.A. County Jails than inmates without immigration holds, despite being, on average, better candidates for pretrial release or other diversion programs.

While immigration holds are requests from ICE that LASD voluntarily hold them beyond their release date to wait for ICE to pick them up, LASD treats them as mandatory orders and detains anyone subject to an ICE hold for days after their release date. These detentions violate the U.S. Constitution and state law, ACLU claimed in the lawsuit.

"Our Constitution guarantees that law enforcement cannot jail residents without probable cause to believe they've broken the law," ACLU staff attorney Jennie Pasquarell said in a statement.

"But LASD holds thousands of people each year beyond their release dates, simply because ICE says they would like to investigate whether they may be removable. In this country, the government can't lock someone in jail at the start of the investigation, it can only do so if investigates and finds good cause to do so," Pasquarell added.

Until now, LASD has refused to allow detainees with an ICE hold to post bail, even when bail had been set by a court, ACLU claimed.

In response to a pre-filing demand letter sent by plaintiffs' attorneys, LASD recognized that individuals subject to ICE holds should be allowed to post bail, have sent bulletins to watch commanders clarifying this rule, and are working on revising policies and data systems to prevent unlawful detentions in the future, according to ACLU.

According to the lawsuit, Duncan Roy, a noted British filmmaker, spent 89 days in Los Angeles Men's Central Jail because the LASD repeatedly refused to allow him to post bail set by the court because Roy was subject to an erroneous ICE hold.

His bail bondsman attempted countless times to post bail to secure his release but each time the LASD jailers told him he could not post bail because of the ICE hold, the lawsuit claimed.

"It's important that people realize that this could happen to anyone," said Roy in a statement.

"It's not just undocumented immigrants. I'm lucky that I can get out and be heard -- many of the people I met in there can't," Roy stressed.

In recent years, LASD has alone detained more individuals on immigration detainers for the purposes of assisting the federal government with its deportation efforts than any other county in the nation, and indeed more than any other state except California and Texas, according to ACLU.