"This is a united front to cause the public to demand answers," said attorney Benjamin Crump.
Two separate violent arrests were caught on tape, and a third confrontation ended with an arrestee dying after a struggle.
"It happens once, you say it's an incident. It happens twice, you scratch your head and you say, 'Well, maybe it's another coincidence.' It happens three times in a month, you say it's a pattern," said Crump.
Crump is sending a letter to Attorney General Eric Holder asking for an independent federal investigation of excessive police force in Los Angeles.
"We want independent eyes looking at this," said Crump.
Video shows Ronald Weekley Jr. apparently being punched by LAPD officers as he was arrested in Venice after skateboarding on the wrong side of the road.
The LAPD says the video doesn't tell the whole story, but Weekley's family intends to sue the department.
"We ask, we demand that charges against my son be dropped," said Ronald Weekley senior.
A lawsuit is also expected from the family of Alesia Thomas. She died in police custody after being arrested inside her apartment. Her family wants to see the LAPD's video of that arrest.
Nurse Michelle Jordan sustained injuries after officers threw her to the ground during an arrest over driving while talking on her cellphone. The Los Angeles County District Attorney isn't prosecuting her case. LAPD Chief Charlie Beck demoted the commander of the Foothill Division because of it. The former commander is now suing the LAPD.
Jordan's attorney also plans to file a lawsuit.
The LAPD said it doesn't respond publicly to lawsuits, but referred Eyewitness News to Beck's previous comments.
"We're taking a number of steps to ensure public confidence and also to ensure these investigations take place appropriately and thoroughly," said Beck.
Weekley Jr. is due in court Thursday morning to face charges of resisting arrest.