Green’s Dictionary of Slang

1. to mark or note as a criminal or suspected person, from a criminal point of view, as a detective.

1834		Sun (N.Y.) 20 June 2/2: The officer observing a ‘Snow Ball’ approaching, who would be likely to ‘spot’ him with the convict, ‘sherried’.
1851		‘Greenhorn’ [G. Thompson] Bristol Bill 45/1: The officer, without knowing who he was, any other than that he was a conspicuous and ‘spotted’ man, immediately took Bill into custody.
1871		Galaxy (N.Y.) Mar. 193: He knew all the shoplifters and pickpockets, and thus was able to ‘spot’ any of them the moment they entered the shop, and so could save the firm and its patrons thousands of dollars every year.
1877		S. James Vagabond Papers (3rd series) 14: One man would throw or push another down after he had kicked the ball, and without [...] provocation. The aggrieved one would ‘spot’ his antagonist and repay in like manner.
1882		Dundee Courier 4 July 7/5: He strongly advised me to return to the North [...] and trust to luck not to be ‘spotted’ by those who had seen me before.
1891		Tuapeka Times (Otago, NZ) 12 Aug. 6/4: A criminal may be ‘spotted’ on account of slang which he uses.
1930		M. Fiaschetti You Gotta Be Rough 65: Her brother was wanted [...] I strolled up to her flat in a tenement to inquire for him. You could tell that she spotted me right off for a dick.

2. to inform against.

1865

Dickens Our Mutual Friend (1994) 159: This man had ‘spotted’ the other, to save himself and get the money.

3. to place a watch on, to observe, to spy on; thus spotting n.

1844		Eve. Mirror (N.Y.) 2 Nov. 2/2: ‘Spotting.’ The last new word on the town is spotting — finding the residence of. A police man tracks a culprit until he ‘spots’ him.
1848		‘Ned Buntline’ Mysteries and Miseries of N.Y. I 80: Don’t stop , sir – don’t stop, or some of ’em will be ‘spotting’ you!
1881		Bulletin (Sydney) 21 May. 9/4: Not a solitary ‘bushy’ would ‘spot’ a horse for even a cake of cheap tobacco.
1887		Bulletin (Sydney) 5 Nov. 13/3: When [the Queen] was a young and ardent maiden she ‘spotted’ her dear Albert, proposed to him right out, and insisted upon hurrying forward an unpopular marriage.
1900		E.H. Babbitt ‘College Words and Phrases’ in DN II:i 63: spot, v. To discover, detect.
1900		Lincs Echo 28 Mar. 3/4: Inspector Basham ‘spotted’ the game, and made the capture of cards, money, etc.
1924		G. Henderson Keys to Crookdom 418: Spot. To point out. To examine a place for future operations. [...] Spot a lay. To prepare a place for robbing.
1935		J. Fishman Sex in Prison 84: The ‘wolves’ or ‘top men’ housed among the normal inmates in the prison, who ‘spot’ those among the younger prisoners whom they wish to make their ‘girls,’ and who ‘court’ them.
1936		D. Maurer ‘Argot of the Und. Narcotic Addict’ Pt 1 in AS XI:2 126/2: To spot for someone. To act as lookout for an addict while he takes a shot in a public place or in a prison where a guard may see him.
1949		Monteleone Criminal Sl. (rev. edn).
1955		‘Blackie’ Audett Rap Sheet 42: Scotty Lawrence had noodled out the general way we would have to take and had men spotting all the ranches in the district.
1965		R.L. Pike Mute Witness (1997) 98: What I should have done, of course, was spot a man at the apartment to catch this guy. [Ibid.] 127: Mary Kelly and Quinleven are still outside spotting the place.

4. (UK Und., also spot off, spot out) to reconnoitre possible sites for future burglary or identify victims for pickpocketing; thus spotted adj.

1865		Leaves from Diary of Celebrated Burglar 54/2: We cood go e-out thru’ t’day and ‘spot-off’ a thing, an’ do it wen we’d a myn to. [Ibid.] 43/1: He [...] was immediately ‘spotted’ out as the ‘flat’ who had before ‘blewed his poke,’ and ‘piped off’ for another ‘dip’. [Ibid.] 19/1: We can ‘spot’ as we go along, and at our return ‘graft’ as many as we can of the ‘drums spotted’.
1866		Night Side of N.Y. 61: When they ‘spot’ a provincial person, or a newly-arrived foreigner, who looks as though it might pay to cultivate his acquaintance, one of the gang will ‘pipe’ or ‘dog’ him, to find out where he puts up.
1885		M. Davitt Leaves from a Prison Diary I 26: To obtain the requisite knowledge of the interior of a place which is ‘spotted’ for operations, the game of ‘sweethearting the slavey’ is gone through by the best-looking member of the gang.
1889		Clarkson & Richardson Police! 314: If a house is ‘spotted,’ some time elapses before all is ripe.
1894		Truth (Sydney) 22 July 2/7: A publican [...] has a racehorse named Derby [...] I have it spotted and you had better go into Boggabri and see if you can spot another.
1918		Jackson Dly News (MS) 1 Apr. 7/3: Crook Chatter [...] ‘“Spotting a joint” is determining a good place to rob’.
1933		Ersine Und. and Prison Sl.
1949		Monteleone Criminal Sl. (rev. edn) 221: spot a lay To prepare a place for future crime.
1950		Goldin et al. DAUL 203/2: Spot, v. 1. To select and mark for robbery; to examine movements of a person or the site of an intended crime.
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.
1982		G. Newbold Big Huey 254: spot (v) Conduct intelligence work prior to committing a crime.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 175/1: spot 2 to conduct intelligence work prior to committing a crime. [...] spot out to keep watch for another while he carries out an illegal activity.

5. (US) to kill, to murder.

1882		B. Harte Flip and Found 24: It’s an even thing if she wouldn’t spot me the first pop [DA].
1926		Odum & Johnson Negro Workaday Songs 150: Han’ on my gun, / Finger on de trigger, / I’s goin’ to jail / ’Cause I’s done spot my nigger.
1934		B. Appel Brain Guy (2005) 195: Holy Christ. McMann spotted. Tough.
1939		R. Chandler Big Sleep 82: At a dollar a rental you take one hundred and twenty-five grand [...] That’s enough to spot a guy for.