He Believes His Lies and it's Pitiful

No, O.J. Simpson does not need to fear running into the person who murdered his ex-wife, Nicole Brown, and Ron Goldman in 1994, because DNA evidence doesn't lie ... so says Nicole's sister.

Tanya Brown tells TMZ ... O.J.'s recent comments about not wanting to go to L.A. because he "might be sitting next to whoever did it" are absurd and disrespectful, but they prove how delusional he really is.

According to Tanya ... all one has to do is look back at the DNA evidence from the murders, which shows the only blood at the crime scene belonged to Nicole, Ron and O.J.

Tanya says, obviously, she does not believe there's another killer out there, but suggests O.J.'s been feeding himself his own lies…