If you're a seasoned movie buff, you might find yourself wondering if any major director has ever seen a ventilation duct.

Crawling through the vents is a classic trope of action movies – but in reality, it would be a tight squeeze for anyone taller than a toddler.

But ventilation experts will never suffer in the cinema the way that lawyers do. Hollywood movies are a riot of wilful inaccuracy when it comes to police procedures and court cases. 

Yes, we know – movies use poetic licence all the time. It's part of what makes them larger than life. It's why they're a form of entertainment and not part of legal training.

Even so, would it hurt for somebody to introduce an objection once in a while, rather than simply barking "Object!"? It would make the legal world so happy – at least until the next time they see a barrister casually wandering around the courtroom.

Look, we're not here to carp or criticise – just to educate and amuse. In that spirit, here are four times that movies got the law downright wrong.

1. Double Jeopardy (1999)

The premise of this crime drama is made clear in its tagline: "Murder isn't always a crime". We're afraid to tell you that it is – although Morrissey, singer of "Meat is Murder", might disagree.

In Double Jeopardy, Libby Parsons wakes up in a blood-soaked yacht with her husband Nick missing. She's convicted of murder – but while serving her time, discovers that Nick faked his death and framed her.

Enter Libby's cellmate, who just happens to be an ex-lawyer – and, let's be honest, no great loss to the profession. She tells Libby that – once freed – she can kill Nick scot-free thanks to the concept of double jeopardy, enshrined in the Fifth Amendment.

Well, we hate to rain on Libby's murderous parade, but the principle of double jeopardy is that you can't be tried for the same crime twice. But if Libby kills her husband years after he faked his death, that's a separate crime and she can most certainly be prosecuted.

Incidentally, double jeopardy isn't forbidden in the UK. The Criminal Justice Act 2003 allows people to be tried twice for the same offence when "new and compelling evidence" is introduced.

2. Intolerable Cruelty (2003)

This black comedy from the Coen Brothers has been described by lawyer and film historian Michael Asimow as "the single most inaccurate movie about the law in all movie history".

It's certainly not kind to lawyers. George Clooney plays a divorce lawyer named Miles Massey, who helps his client to strip her husband of his assets – all based on a cocktail of lies.

But that's not inaccurate as such. Amoral lawyers do exist (or so we hear). But the film strays into outright inaccuracy in its depiction of family law.

The film's plot rests on the factual error that California has "fault divorce" – in other words, divorces where one partner needs to be at fault, following which the unfaithful spouse loses their assets.

In fact, California was the first state in the USA to adopt no-fault divorce in 1973 – and here in the UK, we're only just catching up.

All you need to get a no-fault divorce is "irreconcilable differences" between spouses. Cheating doesn't come into it. However, the film is happy to present the opposite.

3. Liar Liar (1997)

Jim Carrey said that filming Liar Liar led to "total exhaustion". It also led to a number of sighs across the legal firms of America.

Now, it might seem ridiculous for us to pick holes in the legal accuracies of a film in which a pathological liar finds himself physically unable to tell a mistruth for 24 hours.

But even within the confines of a fantastical romp, it gets things badly wrong. Carrey's liar-lawyer is representing a gold-digger named Samantha Cole who is trying to bleed her ex-husband dry. (So far, so progressive.) The main witness is the man she's been cheating with – and he's keen to lie his way to a settlement.

Carrey's character can't deny that Samantha was adulterous, but he successfully proves that her prenup was signed as a minor without parental consent – thereby voiding her marriage and affording her half of her ex's assets.

This rests on the fiction that her prenup could be invalid but her marriage still valid – when in fact, they're both either void or valid.

4. Mrs Doubtfire (1993)

Mrs Doubtfire is a heartwarming, feel-good film about a divorcee, played by Robin Williams, who just wants to be close to his children. But taken at face value, isn't his behaviour a bit dodgy?

Williams's character pretends to be a housekeeper named Mrs Doubtfire as a way of infiltrating his ex-partner's home and spending some quality time with the children.

When you start to see his behaviour as fraudulent, even the tagline "A blessing… in disguise" seems a little sinister.

No matter how charming his Scottish accent, Mrs Doubtfire could be found guilty of impersonation – and potentially premeditated murder, given that he spikes his love rival's meal to cause an allergic reaction.

If custody arrangements mean you're not spending enough time with your children, there are better ways to go about it. Trust us, we're professionals.

Honourable mentions

It's not all bad. Credit's due to The Social Network (2010) with its surprisingly accurate portrayal of a deposition – a less-than-glamorous side of the law that usually gets glossed over. Meanwhile, clips from My Cousin Vinny (1992) have been used to teach legal concepts to law students.

Besides, it's probably for the best that filmmakers take some liberties with the law. After all, a huge part of the job isn't much fun to watch – essentially, a lot of reading, thinking and writing to ensure the best outcome for clients. 

At Milners Law, we pride ourselves on our knowledgeable, no-nonsense approach. Looking for legal support in Yorkshire – or anywhere in the UK? Please get in touch for a free, no-obligation consultation.