[ Pobierz całość w formacie PDF ]
[MUSIC]We wrote this question a few years ago,this is the Ang Mo Kio case.It's a completely made up case, andany resemblance to any realcases is purely coincidental.So we set the case in Ang Mo Kio.Ang Mo Kio is a fairly typicalSingapore neighbourhood, and I thinkwe chose Ang Mo Kio largely becauseit's a fairly typical neighbourhood.So let's have a look at the informationthat's being given. So it's early morning,it's four o'clock.The police enter an apartment.They find a woman in there who's dead,and you're given some informationfrom the pathologist.So clearly, this woman has been beaten.You're given some informationabout the body temperature.A little bit about the state of Rigor Mortis.And then we have some informationfrom witnesses, and some ofthis information from witnesses concernsthe timing of the different events.And finally, there's some DNA evidence.So, we wrote this question particularly totest three particular areas of knowledge.We want to test your understandingof time of death estimation.We want to test your abilityto interpret DNA evidence.And as you'll see later fromthe diagram of this apartment,we're interested in seeing what youunderstand about blood spatter analysis.So let's look at the questions.First one, what marks would youexpect to find on the attacker?Well, this is a fight between a man anda woman, and from the information given,you know that they've been able to extractsomebody's DNA from underneath herfingernails. So what you can concludefrom that is that in the fight,she must have scratched her attacker,and therefore, what you'd expect tofind on the attacker is scratches.In the information given, you can alsosee there is a lot of spilled coffee,so we would also acceptan answer such as coffee stains.That's quite logical.Okay, the apartment has a door,the door of course has a door handle.So now we're asking the question,what additional evidence mightbe found on the door handle?And this is the answer we'd expect,fingerprints, because you have touse your hand to open the door.And if you think about the scene thatwe've set up in this Ang Mo Kio case,it would appear to be an unprovoked,un-premeditated attack, so the attackerwouldn't have made any precautionsto avoid leaving his fingerprints.There are other possible answersthat people might give, butfingerprints is the one that we werereally having in mind at this point.There was presumably a weaponused to attack this woman, butfrom the information you're given, there'sapparently no weapon in the apartment.So we're asking the question, where isthe likely place to find the weapon?And this is why in the diagram ofthe apartment, you find a broken window.It's a broken window, butthe broken glass is outside the window,not inside in the apartment.So clearly something's beenthrown out through the window, soperhaps it was the weapon.So, a likely place to find the weaponis outside the broken window.You see in the apartment,there is an ashtray.The ashtray is sitting neatly on the table,there are no blood stains on the ashtray,or on the table under the ashtray.So, if you're thinking that maybethe ashtray was the weapon,then you're probably thinkingin the wrong direction.If it was the weapon, it wouldn't havebeen put neatly back on the table, andit would be bloodstained.Now, question number four is not sucha direct question as the others.What parts of the evidence doyou consider to be unreliable?So, in order to answer this question,you have to weigh up all ofthe evidence presented, and essentially,you need to look for what evidenceis inconsistent with the other evidence,or even contradicting the other evidence.And the part of the case where youhave the most items of evidence is in the timing.So, the police were called because ofa disturbance in the apartment, andthat disturbance happened at 10 p.m.,this is what the neighbours reported.The next piece of timing evidence we haveis about estimation of the time of death.You're given the body temperaturewhen the body is found,you're given the normal body temperature,and then we can do the arithmetic andwork out how long the victim has been dead.And if you work out the arithmetic,you will see that this victim has beendead for between approximately five to seven hours.That's five to seven hoursfrom the time when the temperaturewas measured, which was 4 a.m.So this places the time of deathbetween 9 p.m, and 11 p.m., and thatmatches nicely with what the neighbourswere saying about this disturbance.The Rigor Mortis is also consistentwith this kind of time frame.What is inconsistent is the final witness sayingthat the sons of the landlord,who have become the suspects,were seen at Jurong Point at 10:20 p.m.So, Jurong Point is the shopping centre nearest toNanyang Technological University.So, we chose Jurong Point forthe question because allour students know where it is.So if the incident happened at 10 p.m.in Ang Mo Kio, which is onthe opposite side of Singapore, andthe suspects were seen at JurongPoint Shopping Centre at 10:20 p.m.,then they have 20 minutes to clean up andcross over to Jurong Point.And when we set up the question,we figured it is not possible to do this.Looking at the answers from the studentswhen we used this question in our exam,it seemed that almost all the studentswere in agreement that it'snot possible to do this in 20 minutes.Though there was one studentwho claimed it was possible,and he knew it was possible because he'd done it.So we thought about giving hisname to the traffic police.Anyway.We have the disturbance at 10 p.m.We have the time of death between 9 and 11 p.m.So of all evidence presented,the part that is probably unreliableis these last witnesses placingthe suspects at Jurong Point at 10:20 p.m.Now, how good is an eyewitness?We've already seen one case in this coursewhere eyewitnesses have been mistaken.And that was in the William Brittle case,in which the jury preferred tobelieve the maggots used in the forensicentomology estimate of time of death,rather than three eyewitnesses.There's another notorious case, wherean eyewitness misidentified a criminal,and this was where a womanmisidentified the man who raped her.He was subsequently imprisonedlargely based on her evidence, butwas later cleared and released.And I came across another casewhere a person misidentified, andthis is a woman who misidentified her own son.She was called by the police to cometo the morgue to identify a body.She identified the body as her own son.It was released, the body was given a proper funeral, andthe next day her son called her.And it turns out that the body wasactually somebody completely different.So what we are saying is,eyewitnesses can be unreliable,and this is pretty much what Locardwas saying in his Exchange Principle.So the next question is asking you toreconstruct the events in the apartmentin as much detail as you can,and here you have to be careful.When we say as much detail as you can,we have to remember we are forensicscientists, so we can only put inas much detail as is supportedby the forensic evidence.We cannot start thinking about motives andthese such things, because usuallythere's no forensic evidence for them.So you have to be very aware here ofwhat forensic science can tell you anddon't go beyond that into imagination.Okay, sowhen we look at the diagram of theapartment, we can see the two coffee cups.So we presume that these two people kneweach other and they were having coffee,which means the first event is that themurderer was admitted by the victim, andof course, there is no sign that anyoneforcibly broke into the apartment either.Then, they were presumably having coffee,some altercation occurred,a fight starts, the cups are dropped,the coffee is spilled, andthat's over there by the table.The first blows are struck along hereon the western wall of the apartment.Now, when we look at the bloodspatter, we can see that the point ofconvergence is fairly high off the floor.So, these first blows were struckwhen the victim was still standing.There was then a trail of blood acrossthe floor to the north wall, andpresumably, this is the victimtrying to get away.The body is then found on the north wall,so that iswhere the victim must have collapsed.From the blood splatter on the north wall,we can conclude that the attack continued, butnow you can see the points of convergenceare fairly low down near the floor.So this woman must have been beaten bythe attacker while she was on the floor,and that is where she died.The final question is, who is the prime suspect?And to answer this question of who isthe prime suspect, you need to usethe remaining piece of evidence that we'vegiven you, which is the DNA evidence.So at the top, you see the DNAextracted from the scrapings fromunderneath the victim's fingernail, andthen, below that, you see theDNA of three of the suspects.The first one is the landlord, Mr. A.So if we compare the DNAfrom underneath the fingernail with Mr.A, we see something very interesting.Because we see that in any given STRfrom the fingernail scrapings,one matches Mr. A and one does not.So the simple conclusion fromthis is that it cannot be Mr.A, because only half of them match.For it to be Mr. A, all of them would have to be matched.Second suspect is Mrs. A.,and once again, we see that there is no match.There's only a partial match.So the conclusion is, it's not Mrs. A.However, you can clearly seethat the DNA from underneaththe fingernails comes fromsomeone who is a child of Mr.and Mrs. A, because of the way the STRs match up.So, it's not Mr. or Mrs. ... [ Pobierz całość w formacie PDF ]