I think KC did her child in, but if I am her defense attorney, here goes one of my theories to try to get KC out of jail.
KC was bedding policemen. This one policeman turned out to be pure evil (was also sex addict just like KC), she met him at Fusion or Sawgrass, or while on patrol at Blanchard Park months prior).
This cop was a child molester (part of child *advertiser censored* ring) but KC did not figure this out until later. The cop said something about missing kids and chloroform in conversation once, but she thought it part of his job, but still it creeped her out, so she searched missing kid websites (and chloroform). KC was a bit wary, but this searching made her feel okay about him.
Maybe KC trusted this cop to watch her child 1 or 2 times at public park for an hour or so, her child liked him, but never all day, or overnight like he was about to do for her on this day. KC was stuck, she got in big fight with CA, and left home with her child. She needed to see her boyfriend. She needed babysitter (slew of calls did not work out). So she ran into cop on her way to TLs with child in car.. She said needed a small favor, (need to work late and find place to live?), he said no problem we'll see you at Sawgrass or Blanchard park next day. Plus her child was so happy to go on "special outing".
But KC didn't know where cop really took her child that day/night really, she dropped child off with cop at the park or by sawgrass steps, how stupid of her, she did not even have his last name or phone number. Did he live at Sawgrass, she did not know, he said he did. (Was he a real cop even or someone posing in uniform, his car was not even marked as she recalled?). Why was she so trusting, because her child liked this guy?
She knew cop was jerk now sure, but still early on, she was not too worried until things dragged on and got very strange. She still didn't think he was really after her or offing her kid! The cop never text or place calls or use computer to contact KC, in previous months they just typically hooked up occasionally when they met while "out", he knew where she liked to hang out and they could arrange to meet. He wasnt giving anyone his number anyway, he was always "on duty".
Anyway, he did not approach her publicly again, but she would find her blackjack missing, making her paranoid so she clung onto TL more, but that is why she goes to her normal hangouts, she is "waiting" to be approached by cop because she knows he won't call her, so she will hopefully hear something, or get some note left on her car, so she can find out what she needs to do. Otherwise, she doesn't know where her child is and thinks she better not report it to missing persons (isn't that where he works?), or she and her family maybe will be missing or dead too. Plus she still wants everything to be ok, and is sure that her child will just show up somehow and this nightmare will be over.
Cop then leaves in her trunk (day she got the neighbor shovel), a small pile of dirt festering with maggots and other fluid. She got the neighbor shovel (dad locked the shed again), drove around to nearest pull off and tried to get dirt and yuk out, some even got on her shoes then, when she returned, went into her own backyard (dna transfer). And it stunk badly of what she did not know. Stuck shovel in pool to clean it off. She stuck her shoes in the pool to try to rid of it. (flustered, she left gate open and ladder in too!). When some of the junk or smell was still on there, she just went barefoot and buried her shoes temporarily into the sandbox. (dna transfer). Then the stupid gas can fell over into residual mess in the trunk, what a waste, she needed that gas, her funds were limited.
KC doesn't know her child is dead for a fact, but she is in shock, blanking out periodically (by early July when TL gets back from NY, this explains her night sweats and her vacant staring with LE, no emotion, she trusts no one). KC wants to go to a "safe" place, boyfriend TL, where there are usually many people around during day/night, and she feels safe with him etc. She goes to get tattoo, as this cop has tattoos, that he got from same place, another thing they had "in common". She is hoping to pick up on some hearsay, this is the way she is "doing her investigation". She takes money from her best friend knowing she may need money for ransom or her own searching. Doing her best to appear normal to TL and not deal with her family until child returns. This is going on way too long, but KC is paralyzed with fear and indecision. She trusts no one.
Cop maybe has threatened her and her family too if she says anything. That is what KC means on her website by "with great power comes great consequence", meaning the police (its a warning, she also thinks CA or GA will figure out this code of hers). KC knows her mother thinks she is deliberately keeping child from her.
KC also says something like "trust no one but yourself", she really knows this from direct experience now. Maybe while she is watching the creepy movies, the cop is planting child body evidence from his afternoon with child, into her trunk. Leaving just enough evidence to get the maggots, dirt and stinky fluids rolling festering.
KC can't open the trunk for GA, because the stain/smell is there; her dad is particular about cleaning cars and will want to know what it is.
KC could not go to the police to report her child missing, as the police were in to protect one of their own in the "kid *advertiser censored* ring", and KC thought child would be killed if she talked. She was afraid she would never see her child again. So she lies a lot mixed in with slivers of truth. Then she decided she would take punishment, that she should have been punished by parents earlier for her gross stealing/lies (this she told to LA). She feels she deserves major punishment. She cannot take plea deal, because she doesnt know where body is.
Now this is stretch but here goes. If guy was real cop and there is a cop *advertiser censored* ring, KC car evidence was then altered further by internal police who reviewed her cell phone and computer searches first before her car being sent away to official FBI labs and Body Farm testing. Pressure is on to solve case quickly. Her chloroform search could also simply be something she looked into after seeing chloroform ad on one of her boyfriends my space. Maybe it was just a joke that was going around. It had no meaning really until LE gave it deadly meaning.