Nathan Matthews (top right) and girlfriend Shauna Hoare (bottom right) are accused of murdering Becky Watts (left)
Prosecutor William Mousley QC said the couple had "lied and lied and lied again" at Bristol Crown Court.
The jury heard Becky's stepbrother Nathan Matthews and his girlfriend Shauna Hoare "did not like her" and wanted her as a "sexual plaything".
Mr Matthews and Ms Hoare deny murdering the 16-year-old.
Mr Matthews admitted he had killed Becky after panicking during an attempt to kidnap and scare her, but insists Miss Hoare had no part in it.
In his closing statement, Mr Mousley told the jury: "The real world where you and I live is a world of good sense and logic, where obvious and safe conclusions can be drawn from the evidence."
He said the world in which the defendants lived was "where lies are told, they are all innocent lies and that fantasy world where nobody tells anyone else what they have done and nobody displays any emotions".
Comment: How long will these repairs hold, and how many other such structurally unsound dams exist that are not being repaired? Questions that almost seem like wasted breathe when the media focuses on irrelevant nonsense like how Russia could 'annihilate' US Army.