There are two offences of conspiracy, a) it is statutory offence to agree with other person or persons for the commission of an offence or offences. b) It is a common law offence to defraud or to outrage public decency. Draco, Cradde, and Goyle wanted to do something to their work colleague Harry, weather it is a physical harm or a psychological harm; it did not matter because they all dislike him. Draco suggested that they should damage his car because that was Harry's main pride. They all agreed to the suggestion made by Draco.
In law, there cannot be a conspiracy unless there is a concluded agreement, an authority for this is Jones (1832) 4B&AD 345 at per Denman CJ. The offence of conspiracy is completed as soon as the parties agree and it is immaterial that they never begin to put it into effect, an authority for this is Paulterer's case (1610) 9 CO Rep 55b, or that the details remain to be agreed, an authority for this is Gill and Henry (1818) 2 B&ALD 2O4. The facts can be applied in this case; therefore, Grabbe, Goyle and Draco are guilty of conspiracy to harm Henry. Criminal damage
You are liable for criminal damage, if you damage a property that belongs to others. Property is damage if it suffers permanent or temporary physical harm or permanent or temporary impairment of it's use or value. If part of a machine remove without which it cannot work, the machine is damage, because it use is impaired. In Roe v Kingerlee (1986), The Division Court held that, graffiti smeared in mud is criminal damage even though it could be wash off, which means that scratching a car even though it can be painted over would be a criminal damage, there for Draco is guilty for criminal damage, because he scratch the car with a coin.
An act does not make a person legally guilty, unless the mind is legally blameworthy. In this case Draco had a mens rea of intend to do the damage, however one can argue that he was intoxicated at the time when committing the offence, the defence of intoxication does not apply in his case because he voluntary intoxicated himself, the offence was going to be committed anyway. An authority for this is Kingston (1994) HL. Caldwell Recklessness Goyle and Draco recklessly damage the car.
A person is "reckless" as to weather or not any property would be destroy or damage, if he does an act which creates an obvious risk that the property will be destroy and when he does the act he either has not given any thought to the possibility of there being any such risk or has recognise that there was some risk involved and none the less gone on to do it. In this case, Draco scratch the car, knowing that it will be damage and Goyle recklessly damage the tires, knowing that the car would not be driven as if it was a normal car. Caldwell test apply to this facts, therefore they are guilty for recklessly causing damages to the car.
Duress However, in the case of Goyle, he can claim the defence of Duress by threat for damaging the tires. 1 The defence of duress by threat is concern with the case where the accuse commits the actus reus of an offence with the relevant mens rea, but is induced to act by the threat made by another person to the effect that unless the accused commits the offence charged, harm will be done to him or another person. The defence of duress by threats can only apply when an offence nominated by the person making the threat. An authority for this is Cole  Crim LR 582 CA Para 22. 34.
If the defence of duress by threat applies, an accused who acted under it can be excuse from criminal liability. This means that, Goyle cannot be liable for the criminal damage to the car as he acted under threat. Draco threatens Goyle to commit the offence, if not, he would break his legs. Draco has a history of violence and Goyle was aware of it, he felt that if he did no commit the offence, Draco would carry out the threat he made to him. There are limitations on type of threat, which can amount to duress. First the threat, which may be express or implicit, must be death or serious bodily harm.
An authority for this is Williamson and Ellerton (1977) 67 Cr App Rep 63, CA. In Singh  1 ALL ER 122,  1 WLR 1600, CA2. Attempt Grabbe is liable to be charge with attempting to cause criminal damage to Henry's car. He puts his hand in his pocket, to get i?? 1 to scratch the car; he accidentally took out every flavour jellybeans instead. For a person to be convicted of an attempt, he must be proved, first to have had an intention to commit that that offence and secondly to have done an act, which constitute the actus Reus of an attempt (s 1. 3.
), an authority for an attempt is Anderson v Ryan (1981), HL. Crabbe clearly had the mens rea to commit the fuller offence; therefore he is guilty for an attempt to commit criminal damage. Quillty of Murder Or Manslaughter? Murder, is an offence for which the only punishment is imprisonment for life, and which is triable only on indictment, is unlawful homicide with" malice aforethought". There are two type of manslaughter. 1. Voluntary; this is where although the accused has killed with malice aforethought, he has done so under circumstances, which the law regards as mitigation the gravity of his offence.
And 2. Involuntary manslaughter is an unlawful killing where the accused has some blameworthy mental state less than an intention unlawfully to kill or cause grievous body harm. Due to the damages to Henry's car, he drove into another vehicle, causing damages to both cars. Henry got injured, the ambulance was delayed because it receive poor direction on to where about was Henry. His injury got infected and three days later he died. A person is guilty of murder if he intended to cause the death or intended to cause seriously personal harm and being aware that he may cause death.
This definition was approved by Lord Stein in Powell; English  AC 147. The act of Dracco,Crabbe and Goyle did not have the mens rea to cause grievous bodily harm or death. Their intention was to cause criminal damages on to the car. They did not foresee death or grievous bodily harm, they did not intent it, however if they did foresee it, but thought that the risk of it accruing was slight and went ahead with the act, they could be liable for murder, but in this case the charge of manslaughter can apply.
An authority for this is Nedrick(1986), CA, it was held that the accused did not have the requisite intent for murder, because he did not foresee death or grievous bodily harm as a virtual certainty; therefore intent could not be inferred. There fore in this case, Draco, Grabbe and Goyle cannot be charge with murder because they did not have the mens rea to commit the offence, hover they can be guilty for manslaughter because their act did contribute to the death of Henry. Intoxication
Crabbe became overcome with fear when Harry was in hospital and took some of his mother's tranquilliser to come him down as a result an adverse reaction to the medicine made him believed that he had a special power to fly and drove his car in access of the speed limit, Crabbe is not liable for his action, he can claim defence of automatism because he is in no control of his actions. An authority for this is Hill v Baxter  1 QB 277.
1. Michael Jefferson-Fifth Edition. Criminal Law 2. Card, Cross and Jones-Thirteenth Edition. Criminal Law 3. Smith & Hogan-Ninth Edition. Criminal Law 4. Richard Cartfed. Criminal Law