Doing some research into Peter Hyatt and his Statement Analysis principles and I think they may be of some help here. I found Hyatt's YouTube interview with Richard D Hall about Madeleine McCann and his work on Katelyn Markam's 911 call to be a revelation. Hyatt shows how emergency service calls or indeed any time a suspect is allowed to speak freely can be vital in determining if that person has guilty knowledge of a crime. He posits a number of theories on the importance of: greetings, priority of information, pronouns, tenses, apologies, concern for victim, and more. On a side note, I find it very interesting that police sometimes release emergency call audio and sometimes do not. In the case of William Tyrrell, the police have chosen to release the audio of the call. I have transcribed it for analysis as Hyatt recommends examining the words.
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000 Call William Tyrrell
Emergency operator - Op
William Tyrrell's Mother - WTM
Op: Police emergency this is Simone.
WTM: Yeah hi my son is missing, he's 3 and a half...
Op: (inaudible)
WTM: Um, Sorry?
Op: Your address?
WTM: Benaroon Drive.
Op: Yes.
WTM: Kendall.
Op: OK Benaroon Drive in Kendall?
WTM: Yes.
Op: Alright I'm just going to bring that up on my map, won't be a moment.
WTM: Thank you.
Op: How long has he been missing?
WTM: I th-, well, I think, well we've been looking in, for him now for about 15 or 20 minutes (Op: OK...) but, ahh... I thought it could be 5, it could be longer cause he was just playing around here, we heard him, and then we heard nothing.
Op: OK, so I've got the nearest cross street being Ellendale Crescent, (WTM: It's, oh...) is that right?
WTM: So-, what is it?
Operator: Ellendale Crescent.
WTM: I don't know my, this is my Mum's house... ah hang on just. There's a another lady out helping us look for him, I'll see if I can find her, but it's Benaroon B-E-N-A-R double O-N.
Operator: Yeah, yeah I can see, I can see where you are I just wanted yeah, so it wa-, it's Benaroon Drive in Kendall and I've just got, I've got your nearest cross as being Ellendale Crescent.
WTM: It could be, I don't know.
Operator: OK. So he's been missing since about 10:30?
WTM: Yeah, I'd say so.
Op: OK, can you describe him to me, how tall, obviously not very tall...
WTM: No, he,(Op interrupts: inaudible) he'd be about 2 and a half feet. He's wearing a Spider-Man outfit.
Op: Yeah, what colour hair has he got?
WTM: Um, he's got, um dark sandy coloured hair, it's short and he's got really big, ah brownie-green coloured eyes.
OP: OK. Would he have had have any shoes on do you know, any, any other distinguishing...features?
WTM: Um, uum, uuum he has, oh he's got a freckle on the top of his head when you part the hair on the left hand side (Op: Yep) you'll see a freckle on the top of his head.
OP: OK. Alright. Do you know where he might have gone?
WTM: Um we're li-, we actually live, well Mum's property's near a State forest... (Op: OK) and they're on huge blocks, we've walked up and down Benaroon Drive... and we can't find him.
OP: OK, what's his name?
WTM: William.
OP: So what's William's Surname?
WTM: Ah Tyrrell T-Y-double R-E-double L.
Op: OK has he been known to sort of go anywhere before?
WTM: No this is the first time (Op: It's the first time he's wandered off?) so it's completely out of character.
Op: There wasn't anyone um suspicious in the area, any vehicles?
WTM: No, no, no, no, well not that I, no, not that I'm aware of.. we were just, I was out there talking with Mum and my... other daughter so...
Op: OK.
WTM: And we her him roaring around the garden and... then I though oh... I haven't heard him I better go... check on him and... can't find him.
Op: OK, alright, we'll send police to see you at Benaroon Drive in Kendall, we'll also get the um a message broadcasted to all the cars to keep a look out for him as well OK?
WTM: Yeah for sure,thanks (inaudible) thanks bye bye.
Op: Bye.
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Peter Hyatt talks to Richard D Hall about Madeleine McCann -
[video=youtube;K0SDo86ws2Q]https://www.youtube.com/watch?v=K0SDo86ws2Q[/video]