Recommended reading - Mute Witness (1963):

Mute Witness

By Robert L. Pike.

Filmed as Bullitt (1968), directed by Peter Yates.

Paperback.

First published 1963.

Published by Bloomsbury Paperbacks

ISBN 13: 9780747578628

ISBN 10: 0747578621

ASIN: 0747578621

Description:

'Rossi isn't dead yet. And from what I hear, the Rossi brothers are pretty tough monkeys.' Clancy's knuckles whitened on the steering wheel. 'Yeah,' he said. 'They're all tough monkeys. Until they lose those precious ten pints...' Lieutenant Clancy, a tough cop from New York's 52nd Precinct, has been handpicked for an assignment. Assistant District Attorney Chalmers needs him to protect a witness whose testimony is vital. That man is Johnny Rossi, an infamous gangster involved in every West Coast racket from prostitution to gambling, who has turned into a whistle-blower. Shacked up in a fleabag hotel, Rossi should be safe. But when a hood with a shotgun breaks past the police guard and blasts Rossi into a critical condition, Clancy has just seventy-two hours to find out why Chalmers can't keep his mouth shut about his so-called secret case, why Rossi came to New York in the first place, who else knows where he is and when they are coming to finish the job off.