Uses of statistics in law

Answer 1

1) When a company is charged with discrimination (e.g. racial or gender), the plaintiff must justify the claim. They typically quote the number of jobs filled and how many of each group (men vs women, white vs black, etc.) were awarded those jobs. Their aim is to show that a certain group (e.g. men or whites) got more of the jobs than they should have. Assuming women were 50% of applicants for a job but men were hired 75% of the time, they might use that as a (statistical) basis for a claim of discrimination. In all fairness, there could be many other reasons for a hiring or promotional bias, but that is beyond the scope of this answer.

2) Bias in application of the death penalty. There have been many claims that black males are given the death penalty more easily than others. Again, this is easily disputable, but that is beyond this scope.

3) Pollution. If cancer rates are (statistically) high around a chemical plant or fracking operation, this can be the basis of a law suit.

4) Education. Claims of "failing schools" are based on comparing student test scores.

5) DNA as evidence. To claim a match in DNA found at a crime scene vs the accused, the prosecutor explains that the chance of anyone matching is, for example, 1 in 100 billion, therefore the accused must be the one who committed the crime.

6) Options fixing. Many company executives were caught getting stock options on days when the company's stock price was surprisingly low based on its running average. By statistics, the prosecutor was able to show that the chance of this happening was vanishingly low, therefore the assignment date must have been chosen retroactively.

7) Accounting Fraud. Certain types of incomes have certain distributions, e.g. dollar amounts start with 1 (e.g. $1.50, $10.23) much more often than they start with 9 (e.g. $9.50, $9.23). So a non-standard distribution of dollar amounts in a database is a strong indicator of fraud.