Actually very few villains take unnecessary chances Jane, and very few would plan a crime and carry it out in such a way that there are only two suspects and they were one of them!
As for getting around at night without lights it's very difficult, because of my job I have been caught out several times so I know.
Criminals do take chances, necessary and unnecessary. They have to take some chances, due to the nature of what they do, and they may take unnecessary chances, due to their own reckless nature, which is why they are criminals in the first place. Jeremy had a reckless nature. Under the right environmental influences, this could have been put to constructive ends: he was probably not aptly fitted for a conservative vocation like farming, but might have found a legitimate trade, profession or vocation that played to his grasshopper nature and recklessness. Instead, Jeremy came under the wrong influences and this came to its head in March 1985, when he broke into the site office at Osea Road and stole money. According to the prosecution case, in words echoed by Maurice Drake at sentencing, Jeremy knew he would come under suspicion for the burglary, but also calculated that his involvement could not be proved. He took the chance. Similarly, during cross-examination by Anthony Arlidge, Q.C., it is claimed that Jeremy said: "That is for you to establish". From one point of view, you can see here a consistent thread of thought, which is a reliance on not being caught, which is quite common to the criminal mentality.
Indeed, criminality often operates pragmatically in the grey area of 'reasonable doubt'. "Say nowt". "They can't prove it". "Stick to your story". Etc., etc.
The criminal may think that he will not be caught or that detection is improbable. To be fair, detection is improbable from a generalised statistical point-of-view. Most crimes go undetected, often not even noticed. On that point, it's interesting that Jeremy carried out the Osea Road burglary in such a manner that it would be noticed. He had staged it in the hope that people would lazily conclude it was an outside job, but he clearly did it this way because otherwise he knew that suspicion would be on him immediately if such a large sum of money were to go missing all at once without an apparent explanation. The staging of a burglary was crude psychology: an attempt to divert focus, but it didn't work. Jeremy would not have seen it as 'taking a chance', as such, but as part of his plan. He did not want to be caught, but knew he would eventually be suspected and relied on the grey area of doubt to see him through.
Turning to the shootings a few months later, if Jeremy is guilty, then he engineered a spectacle outside the farmhouse for the purpose of establishing an alibi. In contrast to the burglary, here he needs to make it look like an inside job. It's no good if the police start developing doubts and thinking it could have been somebody from outside. He believed that the police would enter the farmhouse, find everybody dead, and conclude that Sheila had shot everybody and herself while he was outside with the police. Indeed, this was the police conclusion. Engineering this required a number of things. For instance, he needed to enter and exit the farmhouse undetected and without leaving forensic traces. He needed to ring the police himself, so that he would be at the scene. This meant he needed Nevill to ring him, not the police. This involved taking a risk, which was that he would be making himself the centre of police attention, but the risk was acceptable to Jeremy because the plan involved many different steps and fail-safes that would divert police suspicion away from him, of which the phone call was just one element. Putting the rifle on Sheila's body after shooting her in the main bedroom was analogous to the conspicuous burglary of the Osea Road site office: it was another a diversion of focus, crude but clever psychology.
However, this is where we come to the first fundamental problem with the prosecution case. There is a problem of logic with this scenario: if the phone is downstairs, how does he get Nevill downstairs? Surely Sheila would kill everybody while they are still in bed? Hence, no phone call, hence Jeremy could be guilty, but maybe she wouldn't have had the chance, and Jeremy is still left with the problem that the phone call has to be made. Maybe there is an argument downstairs first? But how does Jeremy ensure Nevill is downstairs rather than in bed? Isn't it risky to allow Nevill to run downstairs? How does he know Nevill will run downstairs? What if Nevill struggles with him upstairs? What then? And why was there a struggle with Nevill downstairs, but not upstairs? The prosecution may say it is because Nevill was drawing fire from the women and boys, but how does Nevill know Jeremy will follow him and not just shoot him or, if out of ammunition, knock him out with the rifle stock? And if he shoots Nevill upstairs, will the police accept that a phone call was made from downstairs first? Maybe what happened is that Jeremy pushed the rifle into Nevill's back and Nevill complied and went downstairs? But if that is what happened, then where is Sheila at this stage? Does the prosecution case depend on her being asleep? We now have somebody in the guilt camp telling us she 'mentally' froze (as opposed to physically), but presumably this is when she is accosted by Jeremy. What is she doing in the meantime? Just sleeping? If she is sleeping, does she never wake? If she wakes, a whole host of other questions enter the picture. Maybe Nevill was downstairs all along and Jeremy incapacitated him first? Perhaps after shooting at him from the stair landing, hence the blood on the kitchen door jamb.
We can see immediately that the initial conclusion of Essex Police, the belief Sheila was the killer, has something important to commend it: it accords with Occam's razor in that it is the conclusion of the fewest parts. She is severely mentally-ill. She is found with the rifle. All the doors and windows are secure. To make Jeremy the killer, we have jump through lots of hoops, answering lots of different questions and solving riddles and problems. These questions, and others, and various problems with the evidence, in my view must lead to a position of reasonable doubt about Jeremy's legal guilt, which means that if he is factually guilty, his plan came dangerously close to succeeding and was only foiled by the doubts of one or two detectives, prompted by the observation of certain highly-subjective and contestable behavioural clues in the aftermath, the evidence of Julie Mugford (to whom he told everything), and the failure of the majority of the trial jury to observe the law and apply the correct standard of proof. Some people will dispute this of course and say that the majority jury decision was correct given the evidence of Julie Mugford. Why did Jeremy take the huge risk of telling her everything? Maybe for the reason I allude to above: he thought that his plan had worked and part of him needed to tell somebody, and Julie was his confederate in crime and close confidant. He was a criminal. He had committed a burglary and was a drug dealer and trafficker of drugs, and according to Liz Rimington, he had floated the idea of burgling houses in Goldhanger. Criminals are reckless and make flawed decisions. That's why they are criminals. Maybe that's all there is to it?