"American Crime Story" tells the real life story of how the late lawyer's client OJ Simpson was acquitted of murder and while Schwimmer got some insight into his character from Robert's ex-wife Kris Jenner, he turned down the chance to speak to Robert's daughters because he did not want to appear on their reality TV show, said The Hollywood Reporter.
"The producers of ['Keeping Up With the Kardashians'] asked me if I wanted to talk to the daughters but I didn't feel that was necessary. And they wanted to do it on camera," he said.
Robert, who died in 2003, defended OJ at his trial where he was accused of the murder of his ex-wife, Nicole Brown Simpson, and her friend, Ronald Goldman.
The case is covered in the new series, "American Crime Story: The People v OJ Simpson", which also stars Selma Blair and Cuba Gooding Jr.