What does 'measuring cast' mean? (1660, UK)

Source: 'Things Necessary to be Continually had in Remembrance', by Sir Matthew Hale (1609-1676)

13. If in criminals it be a measuring cast, to incline to mercy and acquittal.

1. How do you decide the lexical class (ie: part of speech) of the bolded, which I do not comprehend because I cannot disambiguate them?

'measuring' can be:
2. an adjective modifying the noun 'cast', or
3. a common noun preceding and modified by the adjective 'cast'.

PS: I encountered the above on p 20 of The Rule of Law (London, Pengiun, 2010) by Tom Bingham.

The term "a measuring cast" goes far back in English usage and evidently originated in connection with the game of bowls. Robert Nares, A Glossary or Collection of Words, Phrases, Names, and Allusions to Customs, Proverbs, &c. (1825) has this entry for the term:

A MEASURING CAST, met. from the game at bowles. A cast of one bowl so like to that of another, that it cannot be determined which is nearest to the jack, or mistress, but by measuring. [Example:] Hast thou done what is disputable, whether it be well done? It is a measuring cast whether it be lawful or no. [Thomas] Fuller, Good Thoughts in Worse Times [1649], p. 28.

To similar effect is the definition in Noah Webster, A Dictionary of the English Language (1828):

MEASURING, ppr. mezh'uring. Computing or ascertaining length, dimensions, capacity or amount.

2. a. A measuring cast, a throw or cast that requires to be measured, or not to be distinguished from another but by measuring. Waller.

In other words, a measuring cast is a cast of the bowl in a game of bowls that results in so close a call between that bowl and another previously cast that one must use a measuring stick to determine which bowl is closer. As applied to Sir Matthew Hale's resolution,

If in criminals it be a measuring cast, to incline to mercy and acquittal.

the sentence means that, if it is a very close call between a finding of guilt and a finding of innocence, Hale will tend to choose the latter.

Henry Traill, Lord Stafford (1906) provides an interesting instance of the expression from the November 1603 trial of Sir Walter Raleigh, which he presents in the following footnote:

¹ Perhaps in the general disuse into which the ancient and stately game of bowls has fallen, the force of this metaphor may not be at once apparent. A "measuring cast," then, is one by which the bowls of two players are left at such nearly equal distances from the "jack" that the difference if any between the two distances is undiscernible by the eye, and the services of the measuring wand have to be called in. "It will go near to being a measuring-cast between us," was Raleigh's retort when Coke [the prosecutor] taxed him with pride at his trial. "There you run me hard, Mr. Attorney," a modern prisoner would have said.

Short Answer

Looking at the surrounding text in Hale’s original (from your source link), the term measuring cast appears to equate rather literally to the more contemporary expression sighting shot. It is an act whose purpose is at least partly to test the environment for future acts.

Here, ‘measuring’ means ‘experimental’, ‘testing’ or ‘probing’.

‘A cast’ in this case means ‘a throw’, in the sense of committing oneself to releasing (say) dice, or a spear from the hand: the object is aimed and released. It is equivalent to the more common idea of taking ‘a shot’.

In context and principle, Hale is talking about the benefit of the doubt: To begin with, let us toss a few stones into the general territory, to see how they fare, and not fling a huge rock at the plaintiff’s head just because the law allows us to.

Essentially, in this statement Hale means that in new areas of legislation or judgment one should err on the side of leniency.

The surrounding parts of Hale’s text suggest that he (or at least his published text) is preoccupied with being professionally conscientious and consistent, and with applying proportionate punishments, so long as we have good evidence for the crime.

The item to which you draw attention recommends that if we cannot clearly see the scale or the measure of the criminal or the crime, then we should be lenient rather than reflexively punitive.

The expression ‘sighting shot’ is defined usefully at oxforddictionaries.com as:

An experimental shot to guide shooters in adjusting their sights:

figurative ‘their bid for the company is only a sighting shot’

Grammar

The expression ‘measuring cast’ is a compound noun. ‘A cast’ means ‘a throw’. It is an individual throw, with connotations of purpose and direction—see many definitions at oxforddictionaries.com. (Connotations of forcefulness are generally overstated, in most contexts.)

This is what a ‘cast’ in fishing means. It is also why we talk about ‘casting’ a spell. It is there in historical accounts of ‘casting dice’. It is still there (scrapingly) in Chewbacca’s ‘bowcaster’ weapon in the Star Wars films.

The word ‘measuring’ modifies or qualifies ‘cast’, in the same sense as ‘sighting shot’, or ‘practice kick’. The two words proceed together and are treated as a single noun.

Analysis

Your source text lists 18 Resolutions held by Hale, proceeding in philosophical style from the overarching first principle of duty (In the administration of justice, I am entrusted for God, the King and Country) to finer levels of empirical detail.

Any given detail of my gloss here might be in error, so I do not recommend direct quotation for academic purposes. With all this the context, however, we find ‘measuring cast’ making a lot of sense.

To paraphrase, then:

1. Duty (as above), therefore...

2. I must be both conscientious and resolute.

3. I shall trust God’s guidance, above my own reasoning.

4. I must not be impelled by my own moral convictions, however I might be provoked.

5. I am on duty here—I must not allow myself to be distracted.

6. I will avoid prejudice for or against anyone, and will hear all of the evidence, before beginning to formulate any judgment.

7. I will be objective not personally engage with what might be the matter at stake [not quite the same as #6] until all has been said.

8. Matters involving human death are naturally emotional for me, but I must never forget my official duty to the country.

9. People (including me) have their own views: that, in itself, is fine.

10. Rich or poor—my judicial duty is the same.

11. I will proceed with conscience, and not respond in any way to public approval or disapproval of my actions.

12. I will not even ask what other people might think: I will proceed in my assigned official duties.

13. If we find ourselves in in new criminal judgment territory, then my judgment will be less severe than it might be, not the maximum.

14. In crimes of mere verbal troublemaking, keep perspective and remember that suitably minor punishments are available.

15. Faced with a proven murderer, inappropriate leniency is, well, inappropriate.

16. Do not ever accept any judicial influence or opinion, from anyone.

17. I shall manage my staff along these lines and with good judgment.

18. I plan not to overindulge personally: it might affect my work.

Hale kicks off with what he sees as the most important general principles, and works down to more detailed matters. He ends up by promising to keep his (legal) staff on the straight and narrow, and not to get lost in overeating.

In the middle he gives some ideas about judicial attitudes to very broad criminal categories, including the very small-time and the very extreme. At #13, he reminds us that we might find ourselves looking at an unclear kind of case, and warns against lazily applying a severe penalty just because that is easy and permitted. His other resolutions provide the context for this.