There were several problems with this event.  First, hiring day labor, and paying under the table. Additionally, his level of experience with this task was completely unknown.   Because he was not a bona-fide contractor with his own insurance, this event was covered on the workers compensation policy. 

Second, recent studies show that many serious injuries and/or fatalities are the result of "Non-Routine Events", meaning tasks that are rarely done in the scope of the business.  This is due in part as the person is inexperienced in the task, it is more complex, and more dangerous.  Not a good combination. 

What to Learn? 

Be smart.  For non-routine and potentially dangerous tasks, it is best to hire an appropriate licensed contractor who has experience in the task.   Also, you should always request that sub-contractors provide you with certificates of insurance and name you as an additional insured.  

What is a certificate of insurance?

A certificate of insurance is a document that gives evidence of the insured's financial ability (via an insurance policy) to respond to a claim. Under most circumstances, no coverage benefits are afforded to the certificate holder; the certificate merely confirms that the subject company carries insurance.

Why are certificates needed?

Certificates give evidence that the other party has appropriate insurance to cover the claims for which they may be responsible.

When are certificates needed?

Certificates are needed when another party (such as a contractor janitorial service, security service, etc.) performs services on your behalf or has your property in their care, custody or control (e.g. leasing your premises or your equipment).

Who should provide the certificate?

The other party's insurance company or "authorized" insurance agent, broker or risk management department should provide the certificate of insurance to you.

What should a certificate include?

I.  Name of insurance company issuing each policy;

2. Named Insured;

3. Address of Named Insured;

4. Description of Coverage;

Sources:

http://www.acord.org/standards/forms/documents/acordcertificatesfaq_201004.pdf

http://www-admn.csun.edu/risk/riskweb_08/contractural-risk-management/certificate-of-insurance.pdf