Arson investigation starts with the fire itself. To create and sustain a fire three factors must be present. The three factors are known as the fire triangle (Peige ed., 1977). The fire triangle consists of oxygen, a fuel source, and heat. In most cases the percentage of oxygen concentration must be above 16% (Peige, ed., 1977). The fuel may be any flammable substance. The heat source needs only to match the ignition temperature of the fuel.
An arson fire involves the introduction of a heat source that can be as simple as a match or as complex as chemicals with very low ignition temperatures (Battle, 1978). By definition a fire is considered an arson fire when all other accidental caused have been ruled out. To say that the cause of a fire was arson and therefore deliberate, the investigator must have sufficient evidence that one of the factors in the fire triangle was tampered with.
Motives for arson can range from attempts to collect insurance money to revenge or intimidation, attempts to cover up a crime, destruction of questionable business records, Pyromania and occasionally suicide (Battle, 1978)(French 1979)(Lane, 1992) The most common type of Arson is a fire set in an attempt to collect insurance money (Lane, 1992) (French, 1979).
As well as interviewing the fire-fighters and other witnesses the investigator will conduct a complete investigation into the insurance policy holder's background and finances (Kennedy, 1977). The investigator will usually start with the insurance agent who wrote the policy. The investigator is looking for evidence of over insured property or recent changes to the policy. The insurance agent may also recall recent questions about the policy the assured may have asked (Kennedy, 1977).
This may bring intrusion to the suspect's privacy, as the investigator collects evidence from the insurance firm and may be the cause of the arson had nothing to do with insurance money.
The witnesses present when the fire started may give the wrong account. What was the colour of the smoke? Different substances produce smoke in a variety of colours, a colour which can indicate what is burning. For example, gasoline produces a yellow or white flame with black smoke (Lane, 1992). Wood produces a yellow or red flame and grey or brown smoke (Lane, 1992). What if the fire took place at night? And the witness said that the cloud was black instead of brown? (Knowing use of false evidence. Rule 3.03(5) and False statements of material fact. Rule 4.01(a)(statements made to anyone else)).
The investigator should stick to more candid methods like using video footage from any witness around.
The investigator may choose to hire a forensic accountant to study bank records, business records and tax returns. A certified document examiner may be used to examine business records and documents that may have been altered (Kennedy, 1977). This may milden any sort of privacy issues if it happens that the arson was not connected to monetary records of the suspect.
Once the investigator has obtained information regarding the evidence that the fire fighters and witnesses observed and a check of the financial records is complete the investigator will examine the results of the physical evidence found once the fire was extinguished. When examining the physical evidence the investigator must be able to rule out accidental causes of the fire in order to establish that the fire was deliberate (Battle, 1978).
In most homicide cases, although relevant and potential admissible, motive is not an element of the offence of the murder. Thus, the prosecution is entitled, but not required, to prove motive. While the prosecution can offer evidence in order to prove a motive, and though some courts view motive evidence as quite probative of guilt, proof of motive alone does not establish guilt. Instead, motive serves as circumstantial evidence showing that a particular person had a reason to commit a criminal offense.
Although modern rules of evidence generally favor the admissibility of evidence, character evidence offered to prove conforming conduct generally is not admissible. Naturally, there are exceptions to the general rule; some character evidence is admissible.
Let's take a case where a wife hires someone to murder her wealthy husband so that she can obtain her husband's wealth. The man hired to do the killing had sexual liaisons with the wife and also happens to be black.
Character evidence ordinarily is disfavored, though, for a number of reasons. It provides slight probative value, and carries a significant potential for unfair prejudice. Because of its circumstantial nature in that it is not directly probative of the issues in a case, it also has the potential to distract and/or confuse a jury. There is also the concern that juries may punish people for their bad character (or reward people for their good character) rather than for the conduct that is the basis of the charge or the defense.
The prosecution in other hand may attempt to call someone who was involved with the defendant in matters that are assumed to have led to the death of the victim. By calling this accomplice, perhaps unnecessary, the prosecutor - intentionally or unintentionally- plays the "race card", thus distracting the jury with extraneous and potentially prejudicial information. Both the defendant and the witness seemingly will be impacted significantly by the prosecutor's decision to offer evidence on the issue of motive.
Even if the evidence is admissible, a significant question remains, namely, should the prosecutor offer it? Prosecuting attorneys who believe the evidence supports the guilt of an accused have every reason to seek a conviction. But in seeking a conviction, the prosecutor still plays a role in ensuring that the defendant receives a fair trial, as prosecutors bear additional, special responsibilities.
Prosecutors are expected to prosecute their cases forcefully, but only while being fair to the accused. Alternatively speaking, prosecutors must seek both to convict the guilty and to exonerate the innocent. Thus, prosecutors should prosecute their cases vigorously, but only if they believe that justice will attend the convictions. Moreover, in prosecuting cases, vigorous though they may be, prosecutors should not violate rules or utilize unfair methods.
Evidence that diverts the jury's attention from the principal, i.e. blaming all the homicides to have resulted from adultery, should be not or if must, presented sensitively. Such evidence may lead to confusion or erroneous fact-finding hence resulting to giving the wrong verdict.
Courts should emphasize the presumption of admissibility, especially when prejudicial evidence is accompanied by a limiting instruction. This avoids the misuse of evidence by the fact-finders and the perceived ineffectiveness of cautionary instructions.
In cases where one is charged with homicide, adultery being the motive, the prosecutor proceeds to give evidence of the defendants adultery on the issue of motive and though professional conscience might suggest that she should accept the stipulation, particulary in light of the injection of a fact into the case. This case of action is not optimal, but the most likely choice (rejection of proffered stipulation) may be the least suitable option. The best can be expected by identifying and addressing the factors that attoneys should weigh when faced with evidence issue compounded by ethical considerations.