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 having traced 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 down, then called the "carabinieri". Before they responded the police arrived, having traced mobile phones found in a garden to Via della Pergola 7.