1) Set honey trap
Private investigator David Ng says he gets occasional requests from wives to "engineer a situation" to trap the husband into cheating.
This is despite knowing the husband has not been unfaithful.
"In such cases, the woman is usually desperate and has tried other methods of ending the marriage," says Mr Ng, who runs DP Quest Investigation Consultancy.
"But I turn them down because it is unethical and there are easier ways of ending a marriage."
2) Measure scratches
They are supposed to spend quality time with the children during the time allotted to them by their ex-spouses.
But matrimonial lawyer Raymond Yeo says he has seen parents who are so bent on proving that the ex-spouse is neglectful that they spend the allotted time scrutinising any marks - from mosquito bites to innocent scratches - on the children's body.
"They want to gather evidence to use as ammunition against the other party," he says.
"Custody decisions are ever-changing and never set in stone, so allegations of abuse can affect outcomes.
"I always advise my clients against taking such a measure, as access to a child is meant for the parent to enjoy the bond, not embark on such a tactic."
3) Tail child and ex-spouse
To prove neglect, some parents hire PIs to keep tabs on their ex-spouses when they are with the children.
"I have been hired to take videos of a parent spending time with the child during his or her allotted time," says PI Davy Chan.
"In some cases, the child is left with a maid, who may be on her mobile phone, distracted, while the child is playing at a playground.
"Such evidence is used by the other parent to show that the ex-spouse is neglecting the child."
4) Quit job
Mr Yeo says he has seen parents jeopardise their careers to win custody.
"I have come across cases where one parent intentionally resigns from her job to show that she can be a better parent, since she can now look after the child full-time," he says.
"In other instances, people deliberately remain jobless so that they don't have to pay maintenance."
5) Disseminate incriminating evidence
For some spiteful ex-spouses, getting evidence of their other half's infidelity is not enough.
Says Mr Yeo: "I have had clients who want to send the evidence that their spouse has been cheating (supplied by the PI) to friends and relatives, to show that their unfaithful spouse was the cause of the marriage breakdown."
This article was first published on July 27, 2014.
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