Teresa's Ex-Boyfriend, Ryan Hillegas
Teresa's ex-boyfriend, Ryan Hillegas, who is shown many times in Making a Murderer — leading a search party, being questioned as a witness in Steven's trial, and speaking to the media — is another Internet favorite for Halbach's murder, particularly because he was never treated as a suspect. From his oddly stoic demeanor and strange body language when interacting with Teresa's brother (and his friend) Mike, to his claim that he simply "guessed" Teresa's voicemail password to listen to her messages, his behavior strikes many as odd at best. Not to mention that he was present at the crime scene on multiple occasions and couldn't remember what time of day (morning, midday, or night) that he had last seen Teresa.
However, there are other theories that would explain both Hillegas's and Halbach's strange behavior. One theory, based on reports that Hillegas has exhibited stalker tendencies toward co-workers, is that Teresa's ex was calling her and leaving desperate messages on her phone — so when she went missing, he was worried that his messages on her phone would seem suspicious or even incriminating. Here's what one Redditor had to say about what may have followed:
After she goes missing, Hillegas (in this scenario) knows he's innocent, but also knows he's been stalking her and has left voice mails that are going to sound incriminating as hell. After all, he probably has her passwords and has been listening to her voicemail all along and knows who she's been sleeping with and has gone ballistic on her about it, etc. So he's wracked with guilt about his stalking AND fears that he's going to be fingered as the killer.
. . .
Hillegas, innocent of the murder but fearful and guilty, tells Mike "Dude, it was me doing the stalking. I'm really sorry, I loved her (i.e. I was obsessed with her), but I SWEAR I didn't kill her, I was _____ at the time," where ____ is an alibi, perhaps an airtight one. In any event, he's believable, and Mike believes him.
Having spilled the beans and with Mike in his confidence, he unburdens himself further by confessing to Mike about stealing/knowing her passwords (could be innocent, dating back to their dating), so off they go on their earnest but shady-to-us-now sleuthing through her voicemail. Ryan's sketchy voicemails indeed are deleted.