Green’s Dictionary of Slang

1. a detective.

1876		Scribner’s Monthly Apr. 911/2: The stockholders and directors, the ‘car-starters’ and ‘spotters,’ [...] were all embalmed in verse and immortalized in song [DA].
1897		Courier (Lincoln, NE) 6 Feb. 1/1: Buying and selling passes and tickets [...] consitutes the vast bulk of the ticket scalper’s business [...] It is a sneaking trade [...] The seller fears he may be dealing with a ‘spotter’.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 148: SPOTTER: a detective or spy of a private firm or department.
1904		Messenger-Inquirer (Owensboro, KY) 23 Oct. 14/5: The spotter had wired ahead. If an officer [...] is keener on the scent of any one thing [...] it’s a boot-legger.
1916		Olpe Optimist (KS) 7 June 4/3: The spotter testified that he had followed the Mexican and even looked under the door.
1922		E. Murphy Black Candle 156: The customs official or the police officer, called a ’tec, comes to match his wits against the contrabandist [...] In return for his pains, the public call him a ‘spotter’ and other ugly names.
1944		E.M. Kahn Cable Car Days 67: ‘Spotters’ were placed in advantageous positions along the road and in the cars, but every method to detect the fare beaters was unsuccessful [DA].
1949		Monteleone Criminal Sl. (rev. edn).
1958		R. Prather Scrambled Yeggs 82: A spotter! A dirty, stinking spotter! You stinking bastard! You dirty son of a bitch!

2. (US Und.) one who searches for suitable places or victims to rob.

1842		Whip & Satirist of NY & Brooklyn (NY) 26 Feb. n.p.: [C]ounted four suckers and a Jew spotter.
1850		‘Ned Buntline’ G’hals of N.Y. 69: The lady looking after him a moment – just long enough to enable the young spotter to take a complete view of her features.
1889		S. Bailey Ups and Downs of a Crook’s Life 143: From these people the professional criminals receive tips and the inside information [...] These men are called ‘Spotters’.
1899		Sketch (London) 22 Feb. 18: ‘Then there’s a committee, they’re spotters, an’ gits the tips on the good jobs to work, an’ they tells us off for the biz’.
1917		(con. 1908) E. Lynn Adventures of a Woman Hobo 87: I tell you they’re no spotters. She has an honest face.
1924		G. Henderson Keys to Crookdom 17: Many servants who are afraid to steal, act as ‘spotters’ for other crooks. They locate the jewels in a house, secure keys for the doors or else plan to leave a door or window unlocked, and deliver this information to an accomplice. [Ibid.] 88: The ‘spotter’ for the gang will ‘spot a lay’ where he thinks there is a good haul.
1931		J. Wilstach Under Cover Man 92: ‘Who’s the spotter?’ growled Ed Wilson.
1941		V. Davis Phenomena in Crime 139: A ‘spotter’ [...] who makes a preliminary inspection of a jewel or fur emporium before the robbery is attempted.
1952		C. Hamilton Men of the Und. 325: Spotter, One who locates persons or places suitable for robbery.
1969		B. Jackson Thief’s Primer 103: As far as using a professional spotter – having someone going out to spot for us and then we give him 25 per cent or something like that – we never did do that.
1981		(con. c.1905) A. Harding in Samuel East End Und. 86: Jimmy used to be the ‘spotter’ for likely jobs in pawnbrokers and jewellers and he would plan getaways.
1982		G. Newbold Big Huey 254: spotter (n) Person paid to reconnoitre, or provide other information concerning a planned crime.

3. an informer, a company spy.

1865		Brookyn Dly Eagle (NY) 21 Aug. 2/5: These ‘spotters’ make a living by riding about all day and reporting to the President of road how many 6 cents ought to be returned [...] making the trade of collecting fares an undesirable business done under surveillance.
1876		Tennessean (Nashville, TN) 8 June 4/4: The proof [...] was obtained through the agency of ‘spotters’ [...] A ‘spotter’ is a railway detective who travels on the train unknown.
1884		Times (Philadelphia, PA) 24 Aug. 2/5: ‘That spotter thinks he’s fly, but he’s not fly worth a cent,’ whispered a dusty conductor on a Market street car.
1893		Akron Dly Democrat (OH) 1 Apr. 1/3: What is a ‘spotter’? A ‘spotter’ is a spy, employed [...] to spy upon street railway and passenger conductors; to report any alleged act of dishonesty.
1899		Devil’s Lake Inter-Ocean (Dakota, ND) 11 Aug. 5/4: The Devil’s lake [blind] pigs were put to sleep ’by order of an outside “spotter”’ [...] The methods of the blind pig ‘spotter’ are such that it is difficult not to look upon him with contempt.
1907		S.F. Call (CA) 23 June 6/1: Of course ‘knocking down,’ that is fare stealing, receives most of a spotter’s attention.
1914		E. Dyson Spats’ Fact’ry (1922) 30: ‘He demands 20 quid, also in the hinterests iv public morality, hotherwise he’ll tell all he knows.’ ‘A spotter!’ cried Goudy.
1931		Irwin Amer. Tramp and Und. Sl. 179: Spotter.–An employee paid to spy on other workers; a company detective, especially when spying on employees, not guarding against thefts by outsiders.
1934		B. Parker Bonnie And Clyde in Hynd (1949) 79: They hate all the laws, / The stool pigeons, spotters and rats.
1962		Ragen & Finston World’s Toughest Prison 819: spotter – An employee paid to spy on other workers.

4. (drugs) a lookout.

1901		J. Flynt World of Graft 61: I tried to gain entrance to a disorderly house and a so-called club, both of which a cabman assured us would furnish us drinks (intoxicating, mind you) after the eleven o’clock closing hour. The ‘spotters’ at the doors turned us down.
1916		J. Lait ‘‘Taxi, Mister!’’ in Beef, Iron and Wine (1917) 140: He is tabbed by ‘spotters’ that walk and peek from behind granite columns.
1924		G. Henderson Keys to Crookdom 418: Spotter. Lookout, advance man, jiggerman.
1930		J. Lait Gangster Girl 129: We got to put on a spotter to office us when B. B. goes out.
1936		Newcastle Sun (NSW) 27 May 7/4: S.P. Glossary [...] Cockatoo, scout or spotter — One who keeps watch and gives the alarm.
1949		Monteleone Criminal Sl. (rev. edn).
1974		G. Radano Stories Cops Only Tell Each Other 145: ‘There can’t be any slip-ups. They may have spotters somewhere and if they make us we’ve wasted a hundred dollars’.
1992		T. Williams Crackhouse 14: When they walk through ‘drug-copping zones’ (drug-selling locations) and see [...] ‘spotters’ watching for and warning of police presence.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 175/1: spotter n. a person who keeps watch, e.g. during a fight, while gambling, taking drugs, or drawing tattoos.