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Michael Jackson died from an overdose of sedatives on 25 June, 2009 at the age of 50.

The death of the music superstar prompted an outpouring of grief from fans around the world and resulted in the singer's doctor, Conrad Murray, being charged with involuntary manslaughter.

We take a look at some of the unresolved issues surrounding the late King of Pop.

In the months before his death, Michael Jackson employed Dr Conrad Murray, a cardiologist with practices in Las Vegas and Houston, as his personal physician.

He was with the singer on the day he died but the doctor has always maintained that nothing he did should have killed Jackson.

On 8 February, 2010, Dr Murray appeared in court in Los Angeles and pleaded not guilty to the charge of involuntary manslaughter.

He has since made two further court appearances in the case and remains on $75,000 (£50,000) bail. He is free to practice medicine, providing he does not administer powerful sedatives, such as Propofol.

Dr Murray is due to appear in court again on 23 August, when Judge Michael Pastor is expected to set a date for a preliminary hearing, which should start within 60 days of that date.

A trial date cannot be set until the process is completed and Judge Pastor has had an opportunity to consider the evidence. Dr Murray could be sent to jail for up to four years if found guilty.

Like Elvis Presley, Michael Jackson remains a hugely powerful commodity from beyond the grave.

According to estimates by music newspaper Billboard, the singer's estate made more than $1bn (£668m) since his death. The publication says album sales have generated about $383m (£259m) and revenue from the film, This Is It, amounted to nearly $400m (£267m).

Jackson's This is It concerts, despite never taking place, also proved to be hugely profitable. Many fans held on to their tickets as souvenirs, instead of refunding them, which brought in about $6.5m (£4.3m), to be shared with the promoter AEG.

The estate also made money from DVD sales, downloads, royalties and ringtones.

It was revealed last week that the estate has agreed to foot the bill for Jackson's memorial service in Los Angeles, with $1.3m (£868,169) to be paid to the City of Los Angeles and the LA Police Foundation.

In death, Jackson achieved the musical comeback that he had yearned for in the latter years of his life.

He was the biggest selling album artist of 2009, with 8.3 million sales, the vast majority of which were posthumous.

In the past year, nearly 9 million of his albums have sold in the US alone, according to chart analyists Nielsen SoundScan.

This is It, the film that documented the singer's rehearsals for his London concerts, is the highest-grossing concert film and documentary in cinematic history.

Sony Music Entertainment will release 10 albums of Jackson's music over the next seven years, including one of previously unreleased material.

Jackson's children, Michael Joseph Jackson Jr. (13), Paris Katherine Jackson (12) and Prince Michael Jackson II (8), commonly known as Blanket, are being cared for by their grandmother, Katherine, who was awarded guardianship in accordance with Jackson's wishes.

The children have largely stayed out of the public eye, with the exception of Jackson's memorial service and the Grammy Awards ceremony.

The children have been schooled at home although it has been reported that Michael Joseph (Prince) will attend a private school from September.

Jackson's fans are an ever-present force at court hearings for Dr Conrad Murray. They claim the charge of involuntary manslaughter is too lenient and have criticised prosecutors on the case.

Many fans have vowed to continue fighting for "justice" for their idol.

"I love him even more than I did already," said Natalia Franco, at a recent hearing.

"It's just now that we're really grasping his message of love and humanitarianism," added Amy Kimes. "On the one-year anniversary I'm very anxious... I'm asking lots of questions of why."