Born to a priest and his wife in Monken Hadley, then in Middlesex, Garrow was educated at his father's school in the village before being apprenticed to Thomas Southouse, an attorney in Cheapside, which preceded a pupillage with Mr. Crompton, a special pleader.

Although not happy in Parliament, having been returned only for political purposes, Garrow acted as one of the principal Whig spokesmen trying to stop criminal law reform as campaigned for by Samuel Romilly and also attempted to pass legislation to condemn animal cruelty.

For much of the 19th and 20th centuries his work was forgotten by academics, and interest arose only in 1991, with an article by John Beattie titled "Garrow for the Defence" in History Today.

[1] David graduated from Aberdeen University with a Master of Arts degree on 1 April 1736, and became a priest of the Church of England, creating a school in Monken Hadley, in what's now the Greater London area.

[2] William Garrow was educated at his father's school in Monken Hadley, The Priory,[3] which emphasised preparing students for commercial careers such as in the East India Company.

Garrow showed potential, being noted as "attentive and diligent in the performance of the technical and practical duties of the office",[6] and Southouse recommended that he become a solicitor or barrister; as a result, when he was 17, he became a pupil of a Mr. Crompton, a special pleader.

As a pupil Garrow studied hard, fastidiously reading Sampson Euer's Doctrina Placitandi, a manual on the Law of Pleading written in legal French.

Although initially shy (during his first debate, the attendees had to force him from his seat and hold him up while he spoke), he swiftly developed a reputation as a speaker, and was referred to in the press as "Counsellor Garrow, the famous orator of Coachmaker's Hall".

[12] His first case was actually as a prosecutor; on 14 January 1784, barely two months after he was called to the Bar, he prosecuted John Henry Aikles for obtaining a bill of exchange under false pretences.

[18] Garrow made much use of jury nullification to limit the punishment for his convicted clients, in a time when many crimes carried the death penalty (the so-called Bloody Code).

The Government planned a series of 800 arrests, with 300 execution warrants for high treason made out and signed, making a particular effort to prosecute Thomas Hardy and John Horne Tooke.

With Garrow prosecuting and Erskine defending, the trial lasted eight days instead of the normal one, and the foreman of the jury was so tense that he delivered the verdict of "not guilty" in a whisper and then immediately fainted.

[26] In 1806, Thomas Picton, the governor of Trinidad, was charged with a single count of "causing torture to be unlawfully inflicted" on 14-year old free woman of color Luisa Calderón; he was brought before the Court of King's Bench under Lord Ellenborough.

The court records run to 367 pages, and Garrow was deeply involved as prosecuting counsel; indeed, his opening speech on 24 February 1806 is considered by Braby to be one of his best.

After his entry into politics Garrow at first paid little attention, not making his maiden speech until 22 April 1806, when he opposed a charge for the impeachment of Marquess Wellesley.

The Attorney General was the senior Crown prosecutor, during a time when the Prince Regent feared liberal changes to the criminal law and Parliamentary structure.

Garrow, as "a mere creature of the Regent", could be trusted to oppose this; rather than the progressive, defensive work undertaken in his early career, this period was one of conservative aggression against the reformers.

[34] In the early 19th century animal cruelty was widespread; Garrow was one of those who found it appalling, and sponsored a bill in 1816 to increase the penalties for riding horses until their severe injury or death.

[49] David William Garrow was educated at Christ Church, Oxford, earning the degree of Doctor of Divinity, and served as one of the Chaplains to the Prince of Wales.

[52] Garrow's estate was valued at £22,000 after his death near Ramsgate, Kent, including £12,000 in the Bank of England, £5,000 in three insurance policies and £5,000 secured by mortgages – a total of £2,509,000 in 2025 terms.

[53] The trust contained his entire estate, with the trustees being Leonard Smith, a merchant, Edward Lowth Badeley of Paper Buildings, Inner Temple and William Nanson Lettsom of Gray's Inn.

[55] Edward Foss described him as "one of the most successful advocates of his day",[56] something linked more to his "extraordinary talent" at cross-examination than his knowledge of the law;[57] Garrow once told a witness before a case that "you know a particular fact and wish to conceal it – I'll get it out of you!

"[58] Lord Brougham, who regularly opposed him in court, wrote that "no description can give the reader an adequate idea of this eminent practitioner's powers in thus dealing with a witness".

[63] It is indisputable that Garrow massively affected the modern, adversarial court system used in several western nations and the rules of evidence, although he was barely aware of it.

Garrow's practice was a further step forward; with his aggressive and forthright style of cross-examination, he promoted a more committed defence of clients, and indirectly reformed the process of advocacy in the 18th century.

[67] In some ways Garrow was far ahead of his time; he coined the phrase "innocent until proven guilty" in 1791,[68] although the jury refused to accept this principle and it was not confirmed by the courts until much later.