Complex sentence: When Kercher did not answer her door, which was locked, Sollecito unsuccessfully tried to break it in then called the "carabinieri", but before they responded police arrived; they had traced to two mobile phones found in a garden to Via della Pergola 7.
Split into simpler sentences: When Kercher did not answer her door, which was locked, Sollecito unsuccessfully tried to break it in then called the "carabinieri". Soon after police arrived, they had traced to two mobile phones found in a garden to Via della Pergola 7.