The Night Stalker

‘Is he using a device to conceal his voice?’ Cohen asked, stepping closer.

Gus shook his head. ‘It doesn’t sound like it. This is pure static. Interference caused by another radio wave electronic device or a bad signal. Whoever made the call was probably standing next to something, or on a spot affected by a signal dip. I’d say the static noise was unintentional.’

‘Can you clean it up?’

‘Of course.’ Gus smiled smugly and turned on the computer monitor to his left. As the recording played again, audio lines vibrated animatedly on the screen. Gus had another handful of Skittles while watching them attentively.

‘OK, let’s tweak this baby a little.’ He clicked a few buttons and slid some faders on the digital equalizer inside the application on his screen. The static noise was reduced by at least 90 per cent. The out-of-breath whisper now came through much clearer. Gus reached for a pair of professional headphones and listened to the whole thing again. ‘OK, now this was deliberate.’

‘What was?’ Cohen craned his neck in Gus’ direction.

‘The forced whisper. Whoever’s voice this is, it isn’t naturally hoarse and whispering soft. And that is clever.’

‘In what way?’

‘Every human voice travels along certain frequencies that are part of one’s personal identity, as identifiable as fingerprints or the retina. They have certain high, low and medium tones that don’t vary, even if you try to disguise your voice by naturally altering it in any way, like a falsetto or baritone or whatever. With the right equipment, we can still identify those tones and match them to someone’s voice.’

‘You have that equipment, right?’

Gus looked offended. ‘Of course I’ve got that equipment. Look around. I’ve got whatever you need for voice identification.’

‘So what’s the problem?’

Gus leaned back in his chair and let out a long sigh. ‘I’ll show you. Place the tips of your fingers just below your Adam’s apple.’

‘What?’

‘Like this.’ Gus placed the tips of two of his fingers on his throat.

Cohen pulled a face.

‘Just do it.’

Reluctantly Cohen copied Gus’ movement.

‘Now, say something, anything, but try to disguise it in some way. . high, low, gravel, child’s voice, it doesn’t matter. When you do, you’ll feel your vocal cords vibrate. Trust me.’

Cohen looked at Gus with a you’ve-gotta-be-kidding-me face.

‘Go on.’

He finally conceded and, putting on an extremely high-pitched voice, recited the opening three lines of Othello.

‘Wow, profound. I never took you for a Shakespeare fan,’ Gus said, suppressing a smile. ‘Did you feel them vibrate?’

Cohen nodded.

‘When we have any sort of vocal cord vibration, then we have those distinct frequencies I told you about. Now, do the same thing but go for a very soft whisper instead.’

Cohen repeated the same three lines in the most delicate whisper he could muster. His eyes narrowed as he looked back at Gus. ‘No vibration.’

‘Exactly,’ Gus confirmed. ‘That’s because the sounds aren’t being formed by your vocal cords, but by a combination of the air being exhaled from your lungs, and your mouth and tongue movements.’

‘Like whistling?’

‘Like whistling. No vibration, no identifiable frequencies.’

‘Smart motherfucker.’

‘That’s what I said.’

‘So this is the best we can do? We still don’t know what he’s saying.’

Gus smiled cynically. ‘You don’t pay me the big bucks just to give you back a tape with undecipherable whispering, do you? What I mean is that because he forced his own voice into a slow, dragging whisper, we won’t be able to clean it or alter it back to its original pitch. So even if you have a suspect, it will be very hard to get a voice match from this. And I’m pretty sure he knew that.’

‘But you’ll be able to alter it enough so we can understand what he’s saying, right?’

A confident smile came back from Gus. ‘Watch my magic.’ He went back to the digital equalizer, twisted a few more buttons and slid some more faders before loading a pitch shifter onto a separate screen. He placed a small section of the audio recording into a constant loop and worked on it for a few minutes. ‘Oh, hello,’ he said, frowning.

‘What? What?’

Gus automatically reached for the Skittles. ‘We’ve got something else. Some sort of faint hissing noise right in the background.’

‘Hissing?’

‘Yeah, something like a frying pan or maybe rain against a distant window.’ He listened to it again. His eyes went back to one of his monitors and he pulled a face. ‘Its frequency is very similar to the static noise. And that messes things up a little.’

‘Can’t you do something with all this?’ Cohen nodded at all the equipment in the studio.

‘Is today stupid-question day? Of course I can, but to properly identify it I’ll have to run it against my library of sounds.’ Gus started clicking away on his computer. ‘All that can take a while.’

Cohen checked his watch and let out a deflated breath.

‘Relax, that won’t affect me cleaning up the whispering voice. That’ll take me no time at all.’ Gus went back to his buttons and faders. A minute later he seemed satisfied. ‘I think I got it.’ He pressed play and rolled his chair away from the mixing desk.

The same whispering voice Cohen and Myers had tried so hard to decipher poured out of the loudspeakers, as clear as daylight.

Cohen’s jaw dropped as he looked at Gus.

‘Motherfucker.’

Thirty

The first thing Hunter did when he and Garcia got back to Parker Center was get a copy of all the photographs taken at Laura Mitchell’s exhibition to Brian Doyle, the IT Unit supervisor at ITD. Hunter knew that potentially every single person in those pictures was a suspect, but his immediate interest was in identifying the stranger who’d swapped phone numbers with Laura. The photograph Hunter had flagged showed a clear enough image of the stranger’s face to allow Doyle to blow it up and run it against the unified police database.

‘That laptop you called about earlier,’ Doyle said as he transferred all of the pictures to his hard drive, ‘the one that was sent to us by Missing Persons about two weeks ago, belonging to. .’ He started searching his messy desk.

‘Laura Mitchell,’ Hunter confirmed. ‘That’s her in those pictures.’

‘Oh, OK. Anyway, we bypassed her password.’

‘What? Already?’

‘We’re fantastic, what can I say?’ Doyle smiled and Hunter pulled a face. ‘We ran a simple algorithm application against it. Her password was just a combination of the first few letters of her family name and her date of birth. Now, you said you needed to have a look at her emails?’