Steve rang the doorbell of Sophia's house at 7:30PM, trying to get back
on with Sophia. But Sophia told Steve that she would not give up the
opportunity to study abroad. Hearing it, Steve was very angry, and they
quarreled again. Impulsively, Steve picked up the small sculpture and
hit Sophia's heard. By the time Steve realized what happened, Sophia had
already died.
After Steve calmed down, he wipeed every corner of the room and left in
a hurry.
That’s why there was only Justin’s fingerprints in the room.
Steve had wiped all the fingerprints off before Justin came.
At 8:50PM, Justin came to Sophia's home to pick up the package.
Since Steve was so flustered that he forgot to close the door, Justin directly got into her home. When he found Sophia was dead, he
took the opportunity to steal something and then left.
What Steve lied was that
in fact he didn't get back on with Sophia. If
they get back on, then Sophia don't need to send Steve's items back to
him anymore, and she would tell Justin that he don't need to come to
pick up the package. Even if they didn't get back on, as long as Sophia
was alive when Steve left, she would let Steve take his own stuff away.
But those things are still in Sophia's home.
So, Steve is the murderer.