It was rather convenient for the prosecution to keep it quiet about Mugford and her pals all being druggies, who mostly have previous convictions for taking or supplying drugs, and all manner of other criminal offences - the prosecution did not want the jury to know about the background of some of their witnesses, because it was an important part of their case that Jeremy got the timing of his call to Julie wrong, in relation to his call from his father, and to the police...
It was al-right for the prosecution to try and paint Jeremy in a poor light, but when it came down to the background of its own witnesses, it left a lot to be desired, since most of them were druggies, and they lived in a building full of bedsits, that could best be described, as a drugs den...