even without her testimony there is enough evidence that sheila could not have committed the crime.master scipio usmc is right but sometimes is very rude when answering peoples posts 
.but he is the master
That's half the case. That Sheila can't have killed herself (and the others) simply proves someone else killed her and the others and framed her.
The other half is proving who killed them and tried to frame her. Jeremy's claim he received a phone call blaming Sheila was a big fat gift to the prosecution. But Julie's testimony accomplished the same thing. Either one alone would suffice but together they are even more powerful. Jurors might be willing to disregard one thing but when you have multiple pieces of evidence proving the same thing they are more reluctant to ignore all of them.
Without both the case would have been someone tried to execute the entire family in their sleep and staged it to make it look like Sheila did it and that the only one with a motive to do such would be Jeremy and he had no alibi so it had to be him. Some would find that sufficient to convict but some would not so it would depend heavily on who made up the jury.
With both Julie's testimony and the phone call claim he would have to be extremely lucky and get a jury full of fools to acquit. Once in a while someone gets lucky and gets such a jury- look at Robert Dursk. The jury bought that he killed someone in self defense then instead of calling police to say he killed the persons in self defense he dismembered the body and disposed of it. Once in a while defendants get lucky and get a large group of morons. But the law of averages are against it. The law of averages are that out of a body of 12 who pass through jury selection no more than 2 will be utter morons, biased beyond belief or susceptible to bribery. What is required to convict in majority cases- 10 of the 12...
Note the small number of cases where there is a hung jury because 3 or more disagree with their counterparts.
