Many drunks pass out and can not remember details from the night before, especially if they are taking any kind of anti-depressant/anti-anxiety medication and many other drugs, legal and illegal will of course, do the same. Many drunks wake up on sidewalks and other places, unaware of how they got there or with whom. So memory lapses can be believed.
He says they had sex? Well, he is covering the DNA from the semen sample and that is all. He raped her and he killed her so she wouldn't report him to anyone. Then he dismembered her in the bath tub with her pruning saw, bagged up the body parts and drove them in her car to Seattle where he dumped them and probably called his ex-GF to come get him, telling her he woke up on the sidewalk and can't remember anything of how he got there.
But, he remembers having sex with her. Out of the whole 'once we got home' night, the one thing he remembers is the one thing to tie him to the murder - the sex.
He has been trouble for a long, long time.
I feel for all the people out there who are genuinely trying to find someone online to share time with or maybe even find love. When these kinds of stories arise, I am sure it is a scary thing for everyone. But, this young lady drove her own car to the date - right? And she let all her friends and family know his name and where she was gong - right? And they had photos of him - right? She was doing all the correct stuff to be prudent so why did she invite him back to her house? Or did she? Did he force her to drive there or follow her in his own vehicle?
I think it would be too coincidental that he left after consensual sex and someone else came along and committed this crime. I know is his story now, but seriously? She had not one, but two, crazies in her life?
Notice that where he was arrested is kinda close to where Mrs. DeBoer's husband works? The DeBoer's house and the park and ride are in roaming range of this guy, as in the culvert. I get a hinky meter telling me he is responsible for more than this murder.