My first question upon viewing this was, "How does the tapeworm know when a host is dead?" They're not extraordinarily complicated creatures. The guy was probably infected with one of two tapeworms: the beef tapeworm (Taenia saginata) or the pork tapeworm (Taenia solia). Both are pretty basic animals, with two outstanding body parts: the scolex, which attaches to the gut and becomes the primary means by which the worm ingests (our) food; and the proglottid, which is a flat segment containing both male and female organs. The tapeworm will continue to add proglottids throughout its life -- beef tapeworms can have 1000 of 'em -- and the terminal proglottid's the one that performs a reproductive function: it breaks off the worm, passes out of the human host, and releases eggs, thus beginning a new lifecycle.
So we're not dealing with animals known for moving around, except in bits and pieces. And in the research I did, I couldn't find any documented instances in which a mature adult tapeworm fled its dead host. I'm inclined to disbelieve CSI's scientific veracity here, if only because I can't believe that in a world where there are an estimated 100 million tapeworm infection cases annually -- some of which inevitably contribute to the death of their host -- we haven't seen the Animal Planet show Peripatetic Parasites where all the dispossessed cestodes are wandering around, looking for a new host. I'm also inclined to wonder: Were the people who wrote this maybe thinking of roundworm (Ascaris lumbricoides) migration, described here in delightfully squirmy detail? I mean, I'm open to documented incidents in which a tapeworm was seen fleeing a dead body, and if you know of any, put 'em in the episode thread. I just haven't been able to find any myself, and it's not for lack of looking. ANYWAY. Did that scene suddenly make you paranoid about your own intestinal flora? Anyone?
Sara swings by Mia's lab for a little girl talk about semen. The semen on the doorknobs is consistent with Trip's DNA. Mia concludes, "What I'm thinking is that Trip put a trophy condom on his neighbor's door, and then transferred a trace of his reproductive material back on to his own doorknob." Sara looks a little weirded out that Mia's so comfortable with the idea of trophy condoms; Mia says wryly, "Sara, I went to college." Well, so did I, and we didn't decorate with prophylactics either, so step off, Mia. Liam comes in right then to share the news that he "just spoke with WLVU's student affairs officer. Apparently Trip's next-door neighbor, Zach Capola, filed several grievances against him. I'm headed over there now." Sara begins to take off and says, "I'll drive." "You always do," Liam says forlornly.
Down in the morgue, Catherine and David are hanging out over Kevin's corpse. "He's got a time of death -- about midday, the day before. The cause of death is less definitive. Cuts and abrasions are superficial, there's no obvious anatomical defect, and at this point, I'm going to have to check the default, cardiac arrhythmia." Catherine prods, "A young man's heart stops and you don't know why?" David's not backing down.