I am sorry it has taken me so long to respond to your question. I will try to deal with the key points and then apply that to Julie Mugford's position.
It is true that there the terms accessory before/after the fact are no longer used in English law (I say English rather than British or UK because I do not know if Scottish or Northern Irish law still uses the old terms). These terms were replaced with the crime of aiding and abetting the principal offender in the commission of the crime. Someone who aids and abets the principal is guilty of the same offence as the principal and is subject to the same penalties. Law students are still taught the old case law on accessories as it still applies to aiding and abetting.
In addition to the possibilty of prosecution for the main offence, someone who aids and abets may be guilty of other specific crimes, such as perverting the course of justice or assisting an offender. Knowledge of an offence does not in itself amount to a criminal offence, nor does silence save in certain specific statutory cases, such as terrorism and money laundering. To be guilty there must be some positive assistance, whether that assistance was before the commission of the offence, during the commission of the offence or after.
In the present case Julie Mugford was at severe risk of being prosecuted for several serious offences, apart from the ones she specically confessed to, namely the burglary at the Osea caravan park, the cheque frauds and the importation and supplying of drugs (for which she would have received a prison sentence and had her career as a teacher wrecked before it began). The more serious offences were murder, perverting the course of justice and assiting an offender. If she is to be believed (and she cannot have it both ways), by her own admission she not only knew of Jeremy's plans for a considerable period before the murders, but also she provided sleeping tablets to Jeremy in order that he could see whether drugging his family as part of the murder plot was a viable option. The fact that it was not viable does not make any difference. On the day itself she was made aware that the murders were to take place but did not so much as protest, let alone take any steps which might have thwarted the plan. If she is to be believed, Julie Mugford must have been in support of what was about to happen. Further assistance was provided after the murders by expressing calming words to Jeremy during the 3.00/3.30 am telephone call. When she arrived at WHF she provided comfort and encouragement to Jeremy in the knowledge of what he had done and this assisted Jeremy in his successful efforts to present himself to the police in a way which supported the proposition that Shela was responsible. When interviewed by the police she gave an account to the police which backed up Jeremy's account. Saying nothing is not an offence. However saying something which does not include accurate details (for example of her conversations with Jeremy over the previous 24 hours) was providing positive assistance to Jeremy.
In case there is any misunderstanding I am not suggesting that I believe Julie Mugford's testimony. However, the police did and on that basis she was at extreme risk of being charged with a very serious offence in addition to the ones to which she confessed. The fear of that prosecution was in my view the major factor in persuading Julie Mugford to tell the police, eventually, what they wanted to hear. She was trapped. There was no turning back. If she did not cooperate she was faced with the prospect of standing trial alongside Jeremy, facing a substantial prison term. She did not come forward voluntarily. She was in fact arrested and held in custody for a period and subjected to intense pressure. The consent of the Director of Public Prosecutions had to be obtained to take the exceptional course of granting her immunity from prosecution in relation to all offences (with not even a formal caution, contrary to what was suggested at trial, meaning she had no criminal record whatsoever), upon the basis of her agreeing to be a proscution witness. It is a very sorry story indeed.
I'm afraid you've got carried away with your statement whoever you are;whilst making sense in the initial stages you drifted off into flights of fancy which make a mockery of your whole argument. It starts to go awry from the second paragraph after you assert that to be guilty Julie must "provide some positive assistance" when there was absolutely none to the Jeremy supporters' chagrin:she neither provided Jeremy with an alibi nor the infamous sleeping tablets which were for Julie's sole use during one of the most stressful periods of a teacher's career,namely teaching practice,and it is dishonourable of you if you hold a position in law to suggest otherwise. It was Jeremy who imported cannabis stuffed in toothpaste tubes from Amsterdam and not Julie,and though she sold the drug on university premises at Jeremy's behest this does not necessarily bar any teacher from a career;indeed there are male teachers who have abused female pupils who have appealed to the Secretary of State and have been further allowed to teach in an all-male environment,which I know anecdotally from colleagues.
On the day of the murders Julie was not warned in advance as you suggest;after a hard day's work she attempted to decipher yet another of Jeremy's riddles with the "tonight's the night..it's now or never" clue which was symptomatic of Jeremy's infantile manner of speaking for the two years she had known him with his "let's get the ball rolling" idiom used ad nauseum,his "bye honey,love you lots",his sending her roses and booking the bridal suite at a top London hotel interspersed with remarks of the crudest calibre,reminding us of Gresham's head Mr. Bruce Logie Lockhart's aphorism that Jeremy was "a relentless tease". If the head of a public school came to that conclusion then don't expect the product of an all girl's grammar school to be any the wiser in interpreting Jeremy's remarks.
Post-murders we have Julie realizing that Jeremy did have a hand in the murders,whether he was the sole perpetrator or proxy driver,which as Mike suggested the" trick of the light story" gave rise to,but it was Julie who carried the guilt for both of them as the murders for Jeremy were not much different than swatting flies. You misrepresent the chronology because Julie told several people including the Bishop's and Michael Deckers the manager of the Frog and Beans before she voluntarily agreed to visit the Police. Had she not done so of course the trial would have proceeded without Julie on the basis of the silencer and blood evidence pushed by the relatives and going on the summing up of the judge Julie's evidence anyway would not have been paramount.
