Does having celebrity "a-listers" ask for leniency help a defendant's cause at sentencing?

The question in the title of this post results in from my afternoon read of The Star Magazine, which has this new article headlined "A-Listers Ask Judge for Leniency in Sentencing of Michael Douglas' Son." Here is the background:

As Michael Douglas' son awaits his sentence for drug trafficking, Cameron Douglas' family members and friends — including his dad, stepmom Catherine Zeta-Jones, grandfather Kirk Douglas — have written letters to the judge asking for leniency for the heroin addict.

After entering a guilty plea to trafficking large quantities of methamphetamine and cocaine in January, the sometime actor — who appeared in It Runs in the Family with his dad and grandfather — will be sentenced next week in Manhattan federal court.  While he faces a minimum 10 years in prison, letters from loved ones beg the judge for a lighter sentence and placement in a drug treatment program — while largely blaming his parents for his massive troubles.

In the more than two dozen letters, many of Cameron's nearest and dearest pointed fingers at his famous father and mother, Diandra Douglas, for his problems.  Family friend Patricia Sullivan-Webb, who says Cameron spent a large portion of his childhood at her home wishing he was one of her sons, remembers Diandra saying of a then 2-year-old Cameron: "'I don't like this child; I don't think I even love him."  Noting that Diandra would go out partying, despite her son begging her not to, and the boy would frequently fall asleep crying on his pillow....

In other letters from the family, screen legend Kirk called his grandson "a pleasant guy who cared for others" and said he hopes to see him rehabilitated "before I die."  Meanwhile, Catherine's handwritten plea described Cameron as a "caring, considerete [sic], worthy human being" who's been an "exceptional" brother to her young children, Dylan and Carys.

Former NBA basketball coach Pat Riley submitted a letter on Miami Heat stationary and socialite Ann Dexter-Jones called Cameron her “surrogate son” and remembers how he was a lonely child who sought “sibling companionship” from her kids – music producer Mark Ronson, DJ Samantha Ronson and designer Charlotte Ronson.

Several months prior to Cameron’s July 2009 arrest, Star exclusively reported that he had been evicted from his home in Los Angeles' Laurel Canyon for failure to pay rent.  When the landlord entered the apartment, classic signs of drug use were discovered in the home, including glassine envelopes and home drug-testing kits, spoons used to heat a substance over the stove and filthy syringes and mirrors covered in white powder.  In 2007, Cameron was charged with felony possession of a controlled substance when police found liquid cocaine in his car.