This is not a routine case. The fact of the matter is, they can LEGALLY collect DNA in California on any felony arrest. It's the special investigations/homicide team handling this case. And, they ain't talking to anybody about their techniques related to this case. For all we know, they did get a court order to collect CL's DNA.
Bottom line, I think it's very very safe to assume that LE already has CL's fingerprints and DNA, one way or another. Still, it may not matter!
If CL was having an affair with EC, it makes perfect sense that his fingerprints and DNA would be all over EC's vehicle. That is a big problem for LE. Even if CL's DNA is found on EC's body at some point in the future, it can still be explained away by the affair. LE absolutely LUCKED OUT that CL stupidly denied the affair early on and then admitted to kissing her. Still, IMO, if they find EC's body and charge CL with murder, he will change his tune in court and openly admit the affair; if for no other reason than to explain his DNA and fingerprints in her vehicle.